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Page 1: AdvancedDiesel With BluePerformance, mercedes, bmw

BMW Service

Technical Training -Product Information.Advanced Diesel withBluePerformance.

Page 2: AdvancedDiesel With BluePerformance, mercedes, bmw

The information contained in the Product Information and the Workbook form an integral part ofthe training literature of BMW Technical Training.

Refer to the latest relevant BMW Service information for any changes/supplements to theTechnical Data.

Information status: June 2008

Contact: [email protected]

© 2008 BMW AGMünchen, GermanyReprints of this publication or its parts require the written approval ofBMW AG, MünchenVH-23, International Technical Training

Page 3: AdvancedDiesel With BluePerformance, mercedes, bmw

Product Information.Advanced Diesel.

Diesel engine for North America

Selective Catalytic Reduction (SCR)

Low pressure exhaust gas recirculation(LP EGR)

Page 4: AdvancedDiesel With BluePerformance, mercedes, bmw

Notes on this Product Information

Symbols used

The following symbols are used in this Product Information to improveunderstanding and to highlight important information:

3 contains important safety information as well as information that isnecessary to ensure smooth system operation and must be adhered to.

1 identifies the end of a note.

Information status and national variants

BMW vehicles conform to the highest safety and quality standards.Changes in terms of environmental protection, customer benefits anddesign render necessary continuous development of systems andcomponents. Consequently, there may be discrepancies between thisProduct Information and the vehicles available in the training course.

This documentation describes left-hand drive vehicles.In right-hand drive vehicles, the arrangement of some controls orcomponents may differ from the illustrations in this Product Information.Further differences may arise as the result of the equipment variants usedin specific markets or countries.

Additional sources of information

Further information on the individual topics can be found in the following:

- Owner's Handbook

- Integrated Service Technical Application.

Page 5: AdvancedDiesel With BluePerformance, mercedes, bmw

Contents.Advanced Diesel.

Objectives 1

Product information and working reference forpractical applications. 1

Models 3

Engine variants 3

Introduction 7

System components 23

Engine mechanical system 23Air intake and exhaust system 25Cooling system 38Fuel preparation system 41Overview of fuel supply system 43Functions of the fuel supply system 47Components of the fuel supply system 51Overview of selective catalytic reduction 60Functions of selective catalytic reductionsystem 72Components of the selective catalyticreduction system 95Engine electrical system 110Automatic transmission 119

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Objectives.Advanced Diesel.

Product information and working reference for practicalapplications.

This Product Information provides informationon the design and function of the M57D30T2US engine.

This Product Information is structured as aworking reference and complements thesubject material of the BMW AftersalesTraining seminar. The Product Information isalso suitable for self-study.

As a preparation for the technical trainingprogram, this Product Information provides an

insight into the diesel engine for the USmarket. In conjunction with practical exercisescarried out in the training course, its aim is toenable course participants to carry outservicing work on the M57D30T2 US engine.

Technical and practical backgroundknowledge of the current BMW diesel engineswill simplify your understanding of the systemsdescribed here and their functions.

1

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2

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Models.Advanced Diesel.

Engine variants

Models with the M57D30T2 US engine at thetime of market launch in Autumn 2008.

1 - BMW 335d 2 - BMW X5 xDrive35d

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335d E90 M57D30T2 2993 90/84 200/2654200

5801750 11/08

X5 xDrive35d E70 M57D30T2 2993 90/84 200/2654200

5801750 11/08

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History of the M57 engineThe M57 engine is by far one of the mostsuccessful engines at BMW. It is fitted innumerous models right across the vehiclerange. It plays the part of the extremelypowerful top-of-the-range engine, for examplein the 3 Series just as effectively as the well-balanced entry class engine in the 7 Series.

10 years have already passed since itsintroduction and many improvements havebeen made during this period. In particular there-engineering that took place in 2002 andagain in 2005 ensure that the M57 engine isstill state-of-the-art.

The following table shows an overview of theindividual models equipped with the M57engine.

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M57D30O0 530d E39 2926 135/184 390 DDE4.0 9/98 3/00M57D30O0 730d E38 2926 135/184 410 DDE4.1 9/98 3/00M57D30O0 330d E46 2926 135/184 390 DDE4.0 9/99 3/03M57D25O0 525d E39 2497 120/163 350 DDE4.0 3/00 2/04M57D30O0 530d E39 2926 142/193 390 DDE4.0 3/00 5/04M57D30O0 730d E38 2926 142/193 430 DDE4.1 3/00 7/01M57D30O0 X5 3.0d E53 2926 135/184 410 DDE4.0 4/01 9/03M57D30O1 730d E65 2993 160/218 500 DDE506 9/02 3/05M57D30O1 330d E46 2993 150/204 410 DDE506 3/03 9/06M57D30O1 530d E60 2993 160/218 500 DDE508 3/03 4/04M57D30O1 X3 3.0d E83 2993 150/204 410 DDE506 9/03 9/05M57D30O1 X5 3.0d E53 2993 160/218 500 DDE506 9/03 9/06M57D25O1 525d E60 2497 130/177 400 DDE509 4/04 3/07M57D25O1 525d E61 2497 130/177 400 DDE509 4/04 3/07M57D30O1 530d E60 2993 160/218 500 DDE509 4/04 9/05M57D30O1 530d E61 2993 160/218 500 DDE509 4/04 9/05M57D30T1 535d E90 2993 200/272 560 DDE606 9/04 3/07M57D30T1 535d E61 2993 200/272 560 DDE606 9/04 3/07

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M57D30O2 730d E65 2993 170/231 520 DDE626 3/05 9/08M57D30O2 330d E90 2993 170/231 500 DDE626 9/05 9/08M57D30O2 330d E91 2993 170/231 500 DDE626 9/05 9/08M57D30O2 530d E61 2993 170/231 500 DDE626 9/05 in productionM57D30O2 530d E61 2993 170/231 500 DDE626 9/05 in productionM57D30O2 730Ld E66 2993 170/231 520 DDE626 9/05 9/08M57D30O2 X3 3.0d E53 2993 160/218 500 DDE626 9/05 in productionM57D30U2 325d E90 2497 145/197 400 DDE606 9/06 in productionM57D30U2 325d E91 2497 145/197 400 DDE606 9/06 in productionM57D30O2 330d E92 2993 170/231 500 DDE626 9/06 in productionM57D30T2 335d E90 2993 210/286 580 DDE626 9/06 in productionM57D30T2 335d E91 2993 210/286 580 DDE626 9/06 in productionM57D30T2 335d E92 2993 210/286 580 DDE626 9/06 in productionM57D30T2 X3 3.0sd E83 2993 210/286 580 DDE626 9/06 in productionM57D30U2 325d E92 2497 145/197 400 DDE606 3/07 in productionM57D30U2 525d E60 2497 145/197 400 DDE606 3/07 in productionM57D30U2 525d E61 2497 145/197 400 DDE606 3/07 in productionM57D30O2 330d E93 2993 170/231 500 DDE626 3/07 in productionM57D30O2 X5 3.0d E70 2993 173/235 520 DDE626 3/07 in productionM57D30T2 535d E60 2993 210/286 580 DDE626 3/07 in productionM57D30T2 535d E61 2993 210/286 580 DDE626 3/07 in productionM57D30U2 325d E93 2497 145/197 400 DDE606 9/07 in productionM57D30T2 635d E63 2993 210/286 580 DDE626 9/07 in productionM57D30T2 635d E64 2993 210/286 580 DDE626 9/07 in productionM57D30T2 X5 3.0sd E70 2993 210/286 580 DDE626 9/07 in productionM57D30O2 X6

xDrive30dE71 2993 173/235 520 DDE626 5/08 in production

M57D30T2 X6xDrive35d

E71 2993 210/286 580 DDE626 5/08 in production

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Introduction.Advanced Diesel.

A diesel engine for North America

Impressive power and performance as well asexemplary efficiency have contributed tomaking BMW diesel engines an attractive aswell as future-oriented drive technology. Thistechnology is now being made available todrivers in North America.

BMW is introducing this diesel technology tothe USA and Canada under the name "BMWAdvanced Diesel". The introduction is anintegral part of the EfficientDynamics

development strategy, which has become asynonym for extremely low CO2 emissions -not surprising when considering its extremelylow fuel consumption. EfficientDynamics isnot solely an instrument for reducing fuelconsumption but rather it is designed as anintelligent entity with increased dynamics. Notwithout good reason the M57D30T2 engine isreferred to as the world's most agile dieselengine.

HistoryIn 1892, Rudolf Diesel applied for a patent forhis first self-igniting combustion engine.Initially, this large, slow-running engine wasintended for stationary operation only. Theintricate engine structure and complicatedinjection system meant production costs werehigh. The first simple diesel engines were notparticularly comfortable and powerful-revvingmachines. It was not possible to mistake thedistinctive sound of the harsh combustionprocess in the diesel engine when cold (dieselknock). Compared to the spark ignition engine,it offered a poorer power/weight ratio,acceleration characteristics and lower specificoutput.

"Miniaturization" could be realized only byimproving materials and the manufacturingprocess during the course of commercialvehicle production. Although the first dieselvehicle was presented as early as 1936, it wasnot before the 1970s that the diesel enginebecame accepted as a viable drive source.The breakthrough came in the 1980s whenthe diesel engine was finally refined enough tobe a real alternative to the spark ignitionengine. At this time, in view of the improveddynamics and acoustics the decision was

made to introduce the diesel engine in seriesproduction vehicles at BMW.

1 - Rudolf Diesel and his engine

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1983

The M21D24 engine introduced for the firsttime in the E28 as the 524td featured anexhaust turbocharger and had a displacementof 2.4 litres. It was derived from the M20 6-cylinder petrol engine and developed 85 kW/115 bhp. Both engines could therefore bebuilt on the same production facilities.

At that time, the performance with a top speedof 180 km/h and acceleration from 0 to 100km/h in 13.5 seconds set new standards in thedynamics of diesel motor vehicles. The 524tdwas therefore given the nickname "Sportdiesel".

This was the first diesel engine at BMW and, atthe same time, the last for a long time in theUS market.

1985

The M21 was also built as a naturally-aspirated diesel engine as from September1985, making it possible to offer a cost-effective "entry-level engine". This enginemade a name for itself in the 324d (E30) as thesmoothest running auto-ignition engine on themarket.

1987

As the world's first carmaker to do so, BMWintroduced the electronic enginemanagement system, the so-called DigitalDiesel Electronics (DDE). Faster and moreexact than a mechanical control system, theelectronics effectively controls:

• Exhaust emission characteristics

• Fuel consumption characteristics

• Noise emission

• Engine running refinement.

2 - BMW 524td with M21 engine

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1991

1991 saw the debut of the newly developedM51D25 engine which, with intercooling andan output of 105 kW/143 bhp was the mostpowerful diesel engine in its class throughoutthe world. It replaced the M21 engine and was

fitted with a crankcase based on a completelynew design.

The engine was offered in the output variants115 bhp and 143 bhp. Exhaust emission andfull load smoke were reduced by a V-shapedmain combustion chamber in the piston.

1994

The M41 engine was the first 4-cylinder dieselengine to be used at BMW. It was derived fromthe M51D25 engine and shared 56 % of itscomponents. New features included the

hollow-cast camshaft mounted in 5 bearingsas well as a cylinder head cover the isolatedstructure-borne noise.

This engine was fitted in various models of theE36 series.

3 - BMW 525tds with M51 engine

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1998

In 1998 BMW built the most powerful 4-cylinder diesel engine - the M47 with directfuel injection.

With 100 kW developed from 2 litredisplacement, a performance level wasachieved which up until then was the reserveonly of petrol engines. This corresponds to aspecific output of 50 kW or 68 bhp.

Motor sport provided the best proof of theefficiency and reliability of the new dieseltechnology. BMW celebrated a historicsuccess on the Nürburg Ring.

With the 320d, a diesel engine won a 24 hourrace for the first time in motor sports history in1998. This victory came not only due to thefact that it needed fewer pit stops for refuellingbut also because the BMW drove the fastestlap times.

4 - BMW 320d with M47 engine

5 - BMW 320d touring car with M47 engine

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1999

The first V8 diesel engine, the M67D40engine, with 4 litre displacement waspresented in the E38 which developed anoutput of 175 kW. BMW proved its technicalauthority with the, at that time, world's mostpowerful passenger vehicle diesel engine with

common rail fuel injection and 2 exhaustturbochargers.

The engine is fitted with a crankcase madefrom high-strength cast iron with vermiculargraphite (GGV), an aluminium cylinder headand a two-piece oil sump.

2001

The M47TU with the second generationcommon rail injection system and DDE5boosted the power output to 110 kW/150 bhp.

The M57D30 engine is a further developmentof the M51D25 engine. It has a cast ironcasing fitted with a light alloy cylinder headwith 4-valve technology. The M57 engine isthe world's first 6-cylinder in-line diesel enginein a passenger vehicle that is equipped with

future-oriented common rail injectiontechnology.

This new, highly complex electronicallycontrolled fuel injection system perfectlysatisfies the demands for high and constantinjection pressure over the entire injectionperiod. The engine offers substantially lowerfuel consumption compared to swirl-chamberengines, superior performance and smoothengine operation under extreme conditions.

6 - BMW 740d with M67 engine

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2004

The M57TU TOP engine with 2-stageturbocharging is introduced as the mostpowerful diesel engine (E60 and E61). Onesmall and one large turbocharger is used in the2-stage turbocharging system. The dieselengine in the 535d develops 40 kW/54 bhpmore than at the same displacement (3.0litres) in the 530d.

The power output is 200 kW/272 bhp. Themaximum torque of 560 Nm is reached at2000 rpm. With this extraordinary engine, LucAlphand won not only the diesel classificationof the Paris-Dakar Rally, but also came fourthin the overall rankings.

7 - BMW 530d with M57 engine

8 - BMW X5 3.0d with M57TU TOP engine

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2005

The M57TU2 engine is fitted in the E65. Inaddition to the increase in output and torque,it boasts the following technical features:

• Reduced weight through aluminiumcrankcase

• 3rd generation common rail system withpiezo-injector and a fuel rail pressure of1600 bar

• Compliance with the exhaust emissionregulation EURO 4 and diesel particulatefilter as standard

• Optimized electric boost pressure actuatorfor the turbocharger with variable turbinegeometry.

2005

The M67 engine in the E65 wascomprehensively reengineered in the sameyear. The aim was to achieve a distinct boostin dynamics by increasing power output andreducing weight. In the case of the M67specifically this aim is reflected in an increase

in power output of 16 % while simultaneouslyreducing the engine weight by 14 % - andachieved without increasing fuel consumption.

This was mainly achieved through a new,lightweight aluminium crankcase and byincreasing the displacement to 4.4 litres.

9 - BMW 730d with M57TU2 engine

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2006

In 2006, the M57TU TOP engine was re-engineered and equipped with the sametechnical details as the M57TU2, such as analuminium crankcase and piezo-fuel injectors.This engine was given the designationM57D30T2. It was introduced simultaneouslyinto the 3 Series as the 335d and in the X3 as

the 3.0sd. This re-engineering resulted infurther-improved power characteristics,enhanced smooth operation and a significantreduction in fuel consumption. This engineforms the basis for re-introducing dieseltechnology into the USA after more than 20years.

10 - BMW 745d with M67TU engine

11 - X3 3.0sd with M57TU2 TOP engine

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LegislationSince the first exhaust emission legislation forpetrol engines came into force in the mid-1960s in California, the permissible limits for arange of pollutants have been further andfurther reduced. In the meantime, all industrialnations have introduced exhaust emissionlegislation that defines the emission limits forpetrol and diesel engines as well as the testmethods.

Essentially, the following exhaust emissionlegislation applies:

• CARB legislation (California Air ResourcesBoard), California

• EPA legislation (Environmental ProtectionAgency), USA

• EU legislation (European Union) andcorresponding ECE regulations (UNEconomic Commission for Europe), Europe

• Japan legislation.

This legislation has lead to the development ofdifferent requirements with regard to the

limitation of various components in theexhaust gas. Essentially, the following exhaustgas constituents are evaluated:

• Carbon monoxide (CO)

• Nitrogen oxides (NOx)

• Hydrocarbons (HC)

• Particulates (PM)

It can generally be said that traditionally moreemphasis is placed on low nitrogen oxideemissions in US legislation while in Europe thefocus tends to be more on carbon monoxide.

The following graphic compares the standardapplicable to BMW diesel vehicles with thecurrent standards in Europe. A directcomparison, however, is not possible as

• different measuring cycles are used and

• different values are measured forhydrocarbons.

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Although the European and US standardscannot be compared 1:1 it is clear thatrequirements relating to nitrogen oxideemissions are considerably more demanding.

Diesel engines generally have higher nitrogenoxide emission levels than petrol engines as

diesel engines are normally operated with anair surplus.

For this reason, the challenge of achievingapproval in all 50 states of the USA had to bemet with a series of new technologicaldevelopments.

12 - Comparison of exhaustemission legislation

Standard Valid from CO[mg/km]

NOx[mg/km]

HC + NOx*[mg/km]

NMHC**[mg/km]

PM[mg/km]

EURO 4 01.01.2005 500 250 300 - 25EURO 5 01.09.2009 500 180 230 - 5EURO 6 01.09.2014 500 80 170 - 5LEV II MY 2005 2110 31 - 47 6* In Europe, the sum of nitrogen oxide and hydrocarbons is evaluated, i.e. the higher the HCemissions, the lower the NOx must be and vice versa.

** In the USA, only the methane-free hydrocarbons are evaluated, i.e. all hydrocarbons withno methane

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Overview of innovations, modifications and special featuresThe following table provides an overview ofthe special features of the M57D30T2 USengine. They are divided into variouscategories.

• New development signifies a technologythat has not previously been used on BMWengines.

• Modification signifies a component that wasspecifically designed for the

M57D30T2 US engine but does notrepresent a technical innovation.

• Adopted describes a component that hasalready been used in other BMW engines.

This Product Information describes only themain modifications to the M57D30T2 enginecompared to the Europe version as well asfundamental vehicle systems specific to dieselengines.

Component New

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RemarksEngine mechanical system 7 Very few modifications have been made to

the basic engine. The modifications thathave been made focus mainly on ensuringsmooth engine operation.

A significant feature, however, is the OBDmonitoring of the crankcase breather.

Air intake and exhaustsystem

7 The most extensive changes were made tothe air intake and exhaust system. Forinstance, low pressure exhaust gasrecirculation (low pressure EGR) is used forthe first time at BMW on the E70.

In addition to other minor adaptations, thereare substantial differences in the sensor andactuator systems.

Cooling system 7 In principle, the cooling system correspondsto that of the Europe versions, however, ithas been adapted to hot climaterequirements.

Fuel preparation system 7 The functional principle of the fuelpreparation system does not differ from thatof the Europe version, however, individualcomponents have been adapted to thedifferent fuel specification.

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Component New

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RemarksFuel supply system 7 The fuel supply system is vehicle-specific

and corresponds to the Europe version.There are, however, significant differences topetrol engine vehicles.

SCR system(Selective CatalyticReduction)

7 The SCR system is used for the first time atBMW. Nitrogen oxide emissions aredrastically reduced by the use of a reducingagent that is injected into the exhaust systemupstream of a special SCR catalyticconverter. Since the reducing agent iscarried in the vehicle, a supply facility, madeup of two reservoirs, is part of this system.

Engine electrical system 7 The engine is equipped with the new DDE7(digital diesel electronics) control unit that willbe used in the next generation diesel engines(N47, N57).

The preheater system also corresponds tothe N47/N57 engines.

Automatic transmission 7 The automatic transmission corresponds tothat in the ECE variant of the X5 xDrive35d.The gearbox itself has already been used inthe US version of the X5 4.8i, however, adifferent torque converter is used for thediesel model.

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Technical dataThe following table compares the M57D30T2US engine with petrol engines that are offeredfor the same models.Designation N52B30O1 N54B30O0 N62B48O1 M57D30T2Type Straight 6 Straight 6 V8 Straight 6Displacement [cm3] 2996 2979 4799 2993Firing order 1-5-3-6-2-4 1-5-3-6-2-4 1-5-4-8-6-3-7-2 1-5-3-6-2-4Stroke/bore [mm] 88.0/85 88.9/84 88.3/93 90.0/84Outputat engine speed

[kW/hp*][rpm]

193/2606600

225/3005800

261/3506250

200/2654200

Torqueat engine speed

[Nm/lbft][rpm]

305/2252500

407/3001400

475/3503500

580/4281750

Governed enginespeed limit [rpm] 7000 7000 6500 4800

Power output perlitre [hp/l] 86.7 100 72.9 89.3

Compression ratio ε 10.7 10.2 10.5 16.5Cylinder spacing [mm] 91 91 98 91Valves/cylinder 4 4 4 4Intake valve ∅ [mm] 34.2 31.4 35.0 27.4Exhaust valve ∅ [mm] 29.0 28.0 29.0 25.9Main bearingjournal ∅ oncrankshaft

[mm] 56 56 70 60

Big-end bearingjournal ∅ oncrankshaft

[mm] 50 50 54 45

Fuel specification [RON] 98 98 98Fuel [RON] 91-98 91-98 91-98 DieselEnginemanagement MSV80 MSD80 ME9.2.3 DDE7.3

Exhaust emissionstandard US ULEVII ULEVII ULEVII LEVII

* SAE-hp

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Full load diagramsTo get an idea of the performance of theM57D30T2 US engine, it is compared to

various petrol engines in the following full loaddiagrams.

By comparing these two 3 litre engines it canbe clearly seen that, despite virtually identical

power output, the maximum torque of thediesel is almost double as high.

13 - M57D30T2 US enginecompared toN52B30O1 engine

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This enormous difference in maximum torqueis also apparent when comparing the

turbocharged 3 litre petrol engine that has aconsiderably higher nominal power output.

14 - M57D30T2 US enginecompared toN54B30O0 engine

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Even the 4.8 litre V8 engine cannot achievethe maximum torque of the 3 litre dieselengine.

However, the decisive factor is the low enginespeeds at which the diesel engine develops

this high torque. This means that more poweris available in this range. In terms of poweroutput, the diesel engine is superior to any ofthese petrol engines up to an engine speed of4000 rpm.

15 - M57D30T2 US enginecompared toN62B48O1 engine

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System components.Advanced Diesel.

Engine mechanical system

Only slight modifications have been made tothe engine mechanical system compared tothe Europe version.

The modifications include:

• Crankcase

• Crankshaft and big-end bearings

• Pistons

• Crankcase breather.

Crankshaft and big-end bearingsOnly lead-free crankcase and big-endbearings are used in the M57D30T2 USengine. This conforms to requirements

relating to environmental protection and thedisposal of end-of-life vehicles.

CrankcaseIn contrast to the Europe version, theM57D30T2 US engine has a largerreinforcement panel on the underside of thecrankcase.

The reinforcement panel now covers four ofthe main bearing blocks for the crankshaft.

In principle, the reinforcement panel serves toenhance the stability of the crankcase.However, the enlargement was realized solelyfor acoustic reasons.

3 Never drive the vehicle without thereinforcement panel. 1

PistonsThe piston pin has a greater offset than in theEurope version. The offset of the piston pinmeans that the piston pin is slightly off centre.This provides acoustic advantages during

changes in piston contact. The acousticadvantages of increasing the offset are furtherdeveloped particularly at idle speed.

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Crankcase breatherThe crankcase breather in the US version isgenerally heated. In addition, operation of thecrankcase breather is OBD monitored (OnBoard Diagnosis). This is because a leakingsystem would produce emissions.

The only probable reason for a leak in thesystem would be that the blow-by pipe is notconnected to the cylinder head cover. Tofacilitate protection of this situation by theOBD, the heating line is routed via a connectorto the cylinder head cover (2). Essentially, thisconnector serves only as a bridge so thatactuation of the heating system is loopedthrough. The plug connection is designed insuch a way that correct contact is made onlywhen the blow-by pipe has been connectedcorrectly to the cylinder head cover, i.e. thecontact for the heating system is not closed ifthe blow-by pipe is not connected to thecylinder head cover. OBD recognizes thissituation as a fault.

3 If the blow-by pipe is not connected to thecylinder head correctly, the OBD will activatethe MIL (Malfunction Indicator Lamp). 1

1 - Blow-by pipe

Index Explanation1 Cylinder head cover2 Blow-by heater connector for OBD

monitoring3 Blow-by heater connector at wiring

harness4 Filtered air pipe5 Intake air from intake silencer6 Blow-by heater connector at blow-

by pipe7 Intake air to exhaust turbocharger8 Blow-by pipe

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Air intake and exhaust system

The M57D30T2 US engine exhibits thefollowing special features in the air intake andexhaust system:

• Electric swirl flaps

• Electric exhaust gas recirculation valve(EGR valve)

• Low pressure EGR

• Turbo assembly adapted for low pressureEGR.

2 - Air intake and exhaust system - M57D30T2 US engine

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Index Explanation Index Explanation1 M57D30T2 US engine 18 Oxidation catalytic converter and

diesel particulate filter2 Intake silencer 19 Exhaust gas temperature sensor

before oxidation catalytic converter3 Hot-film air mass meter (HFM) 20 Oxygen sensor4 Compressor bypass valve 21 Wastegate5 Exhaust turbocharger, low pressure

stage22 Turbine control valve

6 Exhaust turbocharger, high pressurestage

23 Exhaust pressure sensor afterexhaust manifold

7 Bypass valve for high pressure EGRcooler

24 Swirl flap regulator

8 High pressure EGR cooler 25 Boost pressure sensor9 Temperature sensor, high pressure

EGR26 Exhaust differential pressure sensor

10 High pressure EGR valve 27 NOx sensor before SCR catalyticconverter

11 Throttle valve 28 Temperature sensor after dieselparticulate filter

12 Charge air temperature sensor 29 Metering module (for SCR)13 Intercooler 30 Mixer (for SCR)14 Low pressure EGR valve with

positional feedback31 SCR catalytic converter

15 Temperature sensor,low pressure EGR

32 NOx sensor after SCR catalyticconverter

16 Low pressure EGR cooler 33 Digital Diesel Electronics (DDE)17 Exhaust gas temperature sensor

after oxidation catalytic converter34 Rear silencer

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Air intake system

Intake air system

The intake air system differs on the E70 andE90. Both vehicles draw in unfiltered airbehind the BMW kidney grille.

On the E90, the intake silencer is located atthe front right of the engine compartment fixed

to the vehicle. On the E70, the intake silenceris fixed over the engine.

3 - Air intake system E70 and E90

Index Explanation Index ExplanationA Air intake system E70 3 Intake silencer (air cleaner housing)B Air intake system E90 4 Hot-film air mass meter (HFM)1 Intake 5 Filtered air pipe2 Unfiltered air pipe 6 Blow-by pipe

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Swirl flaps

The engine is equipped with the familiar swirlflaps in the tangential port. A special feature on

the US engine is the electric actuating systemwith positional feedback.

This system provides advantages in terms ofcontrol, however, it is also a prerequisite formeeting OBD requirements.

4 - Intake manifold with electric swirl flaps

Index Explanation Index Explanation1 Linkage for operating the swirl flaps 5 Swirl port2 Connection to throttle valve 6 Tangential port3 Intake manifold 7 Swirl flaps4 Electric motor

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Exhaust system

5 - E70 and E90 exhaust systems

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Index Explanation Index ExplanationA Exhaust system E70 6 SCR catalytic converterB Exhaust system E90 7 NOx sensor after SCR catalytic

converter1 Oxygen sensor and concealed

exhaust temperature sensor beforeoxidation catalytic converter

8 Rear silencer

2 Exhaust gas temperature sensorafter oxidation catalytic converter

9 Exhaust gas temperature sensorafter diesel particulate filter

3 Differential pressure sensor 10 Metering module4 NOx sensor before SCR catalytic

converter11 Diesel particulate filter

5 Mixer

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Exhaust gas recirculation (EGR)Exhaust gas recirculation is one of theavailable options for reducing NOx emissions.Adding exhaust gas to the intake air reducesthe oxygen in the combustion chamber, thusresulting in a lower combustion temperature.

The EGR systems in the E70 and E90 differ.Both vehicles are equipped with the familiarEGR system. Due to its higher weight, the E70additionally features low pressure EGR, usedfor the first time at BMW.

Low pressure EGR

The known EGR system has been expandedby the low pressure EGR on the E70. Thissystem offers advantages particularly at highloads and engine speeds. This is why it is used

in the heavier E70 as it is often driven in thehigher load ranges.

The advantage is based on the fact that ahigher total mass of exhaust gas can berecirculated. This is made possible for tworeasons:

• Lower exhaust gas temperature

The exhaust gas for the low pressure EGRis tapped off at a point where a lowertemperature prevails than in the highpressure EGR. Consequently, the exhaustgas has a higher density thus enabling ahigher mass.

In addition, the exhaust gas is added to thefresh intake air before the exhaustturbocharger, i.e. before the intercooler,where it is further cooled. The lowertemperature of the total gas enables ahigher EGR rate without raising thetemperature in the combustion chamber.

• Recirculation before the exhaustturbocharger

Unlike in the high pressure EGR where theexhaust gas is fed to the charge air alreadycompressed, in this system the exhaust gasis added to the intake air before the exhaustturbocharger. A lower pressure prevails inthis area under all operating conditions.This makes it possible to recirculate a largevolume of exhaust gas even at higherengine speed and load whereas this islimited by the boost pressure in the highpressure EGR.

6 - Low pressure EGR

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The following graphic shows the control of theEGR system with low pressure EGR:

As already mentioned, the low pressure EGRhas the greatest advantage at higher loads andis therefore activated, as a function of thecharacteristic map, only in this operatingmode. The low pressure EGR, however, isnever active on its own but rather alwaysoperates together with the high pressure EGR.

Added to this, it is only activated at a coolanttemperature of more than 55 °C. The lowpressure EGR valve is closed as from a certainload level so that only the high pressure EGRvalve is active again. This means the EGR rateis continuously reduced.

7 - Control of EGR system

Index Explanation Index Explanation1 No exhaust gas recirculation 3 High and low pressure EGR are

active2 Only high pressure EGR is active

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The low pressure EGR system is located onthe right-hand side on the engine directly nextto the diesel particulate filter and the lowpressure stage of the turbo assembly. The

exhaust gas is branched off directly after thediesel particulate filter and fed to the intake airbefore the compressor for the low pressurestage.

8 - Installation position LP EGR

Index Explanation Index Explanation1 Diesel particulate filter 4 Low pressure EGR2 Turbo assembly 5 Exhaust system3 Exhaust turbocharger, low pressure

stage

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9 - Low pressure EGR intake

Index Explanation Index Explanation1 Low pressure EGR valve 3 Low pressure EGR port2 Compressor, low pressure stage 4 Unfiltered air intake

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The following graphic shows the componentsof the low pressure EGR:

There is a fine meshed metal screen filterlocated at the exhaust gas inlet from the dieselparticulate filter to the low pressure EGRsystem. The purpose of this filter is to ensurethat no particles of the coating particularly in anew diesel particulate filter can enter the lowpressure EGR system. Such particles would

adversely affect the compressor blades of theexhaust turbocharger.

3 The metal screen filter must be installedwhen fitting the low pressure EGR cooler tothe diesel particulate filter otherwise there is arisk of the turbocharger being damaged. 1

10 - LP EGR components

Index Explanation Index Explanation1 Temperature sensor,

low pressure EGR5 Coolant infeed

2 Low pressure EGR valve 6 Coolant return3 Connection for positional feedback 7 Low pressure EGR cooler4 Vacuum unit for

low pressure EGR valve8 Sheet metal gasket with filter

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High pressure EGR The exhaust gas recirculation known to date isreferred to here as the high pressure EGR inorder to differentiate it from the low pressureEGR.

Compared to the Europe version, the highpressure EGR is equipped with the followingspecial features:

• Electric EGR valve with positional feedback

• Temperature sensor before high pressureEGR valve

• EGR cooler with bypass.11 - High pressure EGR

12 - High pressure EGR system

Index Explanation Index Explanation1 Coolant infeed 5 High pressure EGR cooler2 High pressure EGR valve 6 Vacuum unit of bypass valve for high

pressure EGR cooler3 Throttle valve 7 Coolant return4 Temperature sensor, high pressure

EGR

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The electric actuating system of the EGRvalve enables exact metering of therecirculated exhaust gas quantity. In addition,this quantity is no longer calculated basedsolely on the signals from the hot-film air massmeter and oxygen sensor but the followingsignals are also used:

• Travel of high pressure EGR valve

• Temperature before high pressure EGRvalve

• Pressure difference between exhaust gaspressure in the exhaust manifold and boostpressure in the intake manifold.

This enables even more exact control of theEGR rate.

The EGR cooler serves the purpose ofincreasing the efficiency of the EGR system.However, reaching the operating temperatureas fast as possible has priority at low enginetemperatures. In this case, the EGR cooler canbe bypassed in order to heat up thecombustion chamber faster. For this purpose,a bypass that diverts the coolant is integratedin the EGR cooler. This bypass is actuated bya flap which, in turn, is operated by a vacuumunit. The bypass is either only in the "Open" or"Closed" position.

Exhaust turbochargerThe US engine is equipped with the samevariable twin turbo as the Europe version,however, the turbo assembly is modified dueto the low pressure EGR.

On the one hand, the inlet for the low pressureEGR is located on the compressor housing forthe low pressure stage. On the other hand, thecompressor wheels are nickel-coated toprotect them from the exhaust gas.

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Cooling system

The cooling system, is in part, vehicle-specific.In principle, there are scarcely any differencesbetween the cooling systems on petrol anddiesel engines.

The two basic differences compared to petrolengines are:

• No characteristic map thermostat

• EGR cooler.

The E70 and E90 differ with regard to the EGRcooler. Since the E70 is equipped with a lowpressure EGR system, it has a second EGRcooler, the low pressure EGR cooler.

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13 - X5 xDrive35d cooling system

Index Explanation Index Explanation1 Radiator

Coolant-to-air heat exchanger10 Heating heat exchanger

2 Gearbox coolerCoolant-to-air heat exchanger

11 Duo-valve

3 Electric fan 12 Auxiliary coolant pump4 Thermostat, gearbox oil cooler 13 Engine oil cooler

Engine oil-to-coolant heat exchanger5 High pressure EGR cooler 14 Expansion tank6 Thermostat 15 Gearbox oil cooler

Gearbox oil-to-coolant heatexchanger

7 Coolant pump 16 Ventilation line8 Low pressure EGR cooler 17 Additional radiator

Coolant-to-air heat exchanger9 Coolant temperature sensor

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14 - 335d cooling system

Index Explanation Index Explanation1 Gearbox cooler

Coolant-to-air heat exchanger9 Heating heat exchanger

2 RadiatorCoolant-to-air heat exchanger

10 Duo-valve

3 Additional radiatorCoolant-to-air heat exchanger

11 Auxiliary coolant pump

4 Thermostat, gearbox oil cooler 12 Engine oil coolerEngine oil-to-coolant heat exchanger

5 High pressure EGR cooler 13 Expansion tank6 Thermostat 14 Gearbox oil cooler

Gearbox oil-to-coolant heatexchanger

7 Coolant pump 15 Ventilation line8 Coolant temperature sensor 16 Electric fan

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Fuel preparation system

15 - Fuel preparation system, M57D30T2 US engine

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The fuel preparation system differs neither interms of design layout nor function from theEurope version. However, some componentshave been adapted to the different fuelspecification.

These components are:

• High-pressure pump

• Fuel rail

• Fuel injectors.

These adaptations are restricted to differentcoatings and materials on the inside.

Index Explanation Index ExplanationA Fuel feed 6 Return lineB Fuel return 7 Feed lineC Fuel high pressure 8 Fuel temperature sensor1 Fuel rail pressure sensor 9 High-pressure line2 High-pressure line 10 Fuel rail3 Leakage oil line 11 Restrictor4 Piezo injector 12 High-pressure pump5 Fuel rail pressure control valve 13 Volume control valve

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Overview of fuel supply system

16 - E90 Diesel fuel supply system

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DesignAs for petrol engines, the fuel system isvehicle-specific. There are, however, severalgeneral and significant differences comparedto petrol engine vehicles.

These are:

• The system includes a fuel return line

• The breather system is significantly simpler

• There is no carbon canister (AKF) and nofuel tank leakage diagnosis module (DMTL)

• There is no pressure regulator

• The fuel filter is not located in the fuel tank.

The design layout of the fuel supply systemsin the E70 and E90 are described in thefollowing.

Index Explanation Index Explanation1 Fuel filler neck 5 Right-hand service opening2 Left-hand service opening 6 Filler vent3 Fuel return line 7 Electric fuel pump controller4 Fuel filter with heating system

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E70 with diesel engine

In addition to delivering the fuel to the engine,the fuel supply system also filters the fuel. Thefuel tank contains an additional ventingsystem.

The fuel tank is divided into two chambersbecause of the space available in the vehicle.The fuel supply system has two delivery units

that are accommodated in the right and leftfuel tank halves.

The fuel pump (3) with intake filter (2) is a partof the right-hand delivery unit. The surgechamber including a suction jet pump (10)with pressure relief valve (11) and initial fillvalve (1) as well as a lever-type sensor (G)complete this delivery unit.

17 - Fuel tank on E70 with diesel engine

Index Explanation Index ExplanationA Fuel filler cap 1 Initial fill valveB Pressure relief valve 2 Intake mesh filterC Non-return valve 3 Fuel pumpD Surge chamber 4 Pressure relief valveE Fuel tank 5 Feed lineF Service cap 6 Return lineG Lever-type sensor 7 Leak prevention valveH Filler vent valve 8 Suction jet pumpI Connection 9 Air inlet valveJ Maximum fill level 10 Suction jet pumpK Non-return valve 11 Pressure relief valveL Filter

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The suction jet pump (8), lever-type sensor(G), leak prevention valve (7) and air inlet valve(9) belong to the left-hand delivery unit.

A line leads from the filler vent valve (H) to thefilter (L). The fuel filler pipe is connected to thisline via the non-return valve (K).

E90 with diesel engine

18 - Fuel tank on E90 with diesel engine

Index Explanation Index ExplanationA Fuel filler cap 1 Initial fill valveB Pressure relief valve 2 Intake mesh filterC Non-return valve 3 Fuel pumpD Surge chamber 4 Pressure relief valveE Fuel tank 5 Feed lineF Service cap 6 Return lineG Lever-type sensor 7 Leak prevention valveH Filler vent valve 8 Suction jet pumpI Connection 9 Non-return valveJ Maximum fill level 10 Suction jet pumpL Filter 11 Pressure relief valve

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Functions of the fuel supply system

Fuel tank

A pressure relief valve (B) is integrated in thefuel filler cap (A) to protect the fuel tank (E)from excess pressure. A non-return flap (C) islocated at the end of the fuel filler neck. Thenon-return flap prevents the fuel from sloshingback into the fuel filler neck.

The components in the fuel tank can bereached via the two service caps (F).

The fuel fill level can be determined via the twolever-type sensors (G).

The surge chamber (D) ensures that the fuelpump always has enough fuel available fordelivery.

19 - Fuel tank for E70 with diesel engine

Index Explanation Index ExplanationA Fuel filler cap E Fuel tankB Pressure relief valve F Service capC Non-return valve G Lever-type sensorD Surge chamber

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Fuel supply system

20 - Fuel supply system for E70 with diesel engine

Index Explanation Index Explanation1 Initial fill valve 7 Leak prevention valve2 Intake mesh filter 8 Suction jet pump3 Fuel pump 9 Air inlet valve4 Pressure relief valve 10 Suction jet pump5 Feed line 11 Pressure relief valve6 Return line

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In the event of the surge chamber beingcompletely empty, the initial filling valve (1)ensures that fuel enters the surge chamberwhile refuelling.

The fuel reaches the fuel pump (3) via theintake filter (2), then continues through thedelivery line (5) to the fuel filter. The fuel pumpis located in the surge chamber. A pressurerelief valve (4) is integrated in the fuel pump toprevent pressure in the delivery line from risingtoo high. As the engine switches off, thedelivery line is depressurized but cannot rundry because, provided the system is notleaking, no air is able to enter it. In addition,after the fuel pump has switched off, the fuelpressure/temperature sensor is checked forplausibility.

Fuel that is required for lubrication and thefunction of high pressure generation flowsback into the fuel tank via the return line (7).The fuel coming from the return line is dividedinto two lines downstream of the leakprevention valve (7). The non-return valveprevents the fuel tank from draining in theevent of damage to lines on the engine or

underbody. It also prevents the return linefrom running dry while the engine is off.

One of the lines guides the fuel into the surgechamber via a suction jet pump (10). Thesuction jet pump transports the fuel from thefuel tank into the surge chamber. If the fueldelivery pressure in the return line increasestoo much, the pressure relief valve (11) opensand allows the fuel to flow directly into thesurge chamber.

An air inlet valve is used in the E70. The airinlet valve (9) ensures that air can enter the linewhen the engine is off, preventing fuel fromflowing back from the right-hand half of thefuel tank to the left.

Instead of the air inlet valve (9) a non-returnvalve is used on the E90. The non-return valveensures that, while the engine is off, fuel fromthe right-hand half of the fuel tank cannot flowback into the left-hand half. The return systemremains completely filled with fuel.

A further line branches off into the left-handhalf of the fuel tank after the non-return valve(7) and transports the fuel into the surgechamber via the suction jet pump (8).

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Air supply and extraction

Fuel ventilation is ensured by means of thefiller vent valve (H).

The filler vent valve is located in the fuel tankand uses the connection (I) to determine themaximum fill level (J). The filler vent valvecontains a float that buoys upwards on the fuelwhen the vehicle is refuelled and blocks thefiller ventilation. The fuel rises in the fuel fillerand the fuel nozzle switches off.

A roll-over valve is also integrated in the fillervent valve to block the ventilation line when acertain angle of incline is reached andprevents fuel from draining out if the vehiclewere to roll over.

The non-return valve (K) prevents fuel fromescaping via the ventilation when the vehicle isrefuelled. During operation, air can flow intothe fuel filler pipe and the fuel can flow fromthe fuel filler pipe into the tank.

The filter (L) prevents dirt or insects fromentering the ventilation and blocking the line.

3 If the ventilation line does becomeblocked, fuel consumption during operationwould cause negative pressure and the fueltank would be compressed and damaged. 1

21 - Tank ventilation system for E70 with diesel engine

Index Explanation Index ExplanationH Filler vent valve K Non-return valveI Connection L FilterJ Maximum fill level

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Components of the fuel supply system

Pressure relief valve in fuel filler cap

The pressure relief valve ensures that, if thereis a problem with fuel tank ventilation, anyexcess pressure that may form can escapeand the fuel tank is not damaged.

If excess pressure forms in the fuel tank, thiscauses the valve head (1) and with it the entirepressure relief valve (5) to be lifted off thesealed housing (6). The excess pressure cannow escape into the atmosphere. The excesspressure spring (2) determines the openingpressure. The excess pressure spring uses adefined pressure to push the pressure reliefvalve onto the sealed housing and issupported by the brace (3).

22 - Pressure relief valve

Index Explanation1 Valve head2 Excess pressure spring3 Brace4 Bottom section of housing5 Pressure relief valve6 Sealed housing

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Protection against incorrect refuelling

23 - Protection againstincorrect refuelling

Index Explanation Index Explanation1 Housing 5 Torsion spring2 Locking lever 6 Rivet3 Tension spring 7 Hinged lever4 Flap 8 Ground strap

24 - Protection againstincorrect refuelling

Index Explanation Index Explanation∅ 21 mm Petrol fuel nozzle ∅ 24 mm Diesel fuel nozzle

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The protection against incorrect refuellingfeature ensures that the fuel tank cannot befilled with gasoline. As the previous graphicshows, only a fuel nozzle with a diameter ofapproximately 24 mm can fit. If the diameter isapproximately 21 mm, the flap (4) does notopen as the hinged lever (7) and the lockinglever (2) cannot be pushed apart.

If a diesel fuel nozzle is inserted, this pushesthe locking lever (2) and the hinged lever (7) at

the same time. The hinged lever is pushedoutwards against the tension spring (3) andreleases the flap (4). This is only possible,however, if the hinged lever cannot movefreely and is also locked in position by the fuelnozzle.

3 To open the protection against incorrectrefuelling feature in the workshop, a specialtool is required. 1

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Fuel pumpToday's diesel vehicles are fitted with electricfuel pumps only. The electric fuel pump isdesigned to deliver a sufficient amount of fuelto lubricate and cool the injectors and thehigh-pressure pump and to satisfy themaximum fuel consumption of the engine. Ithas to deliver the fuel at a defined pressure.That means that when the engine is idling orrunning at medium power, the fuel pump

delivers several times more than the amountof fuel required. The fuel pump deliversapproximately three or four times the volumeof maximum possible fuel consumption.

The electric fuel pump is located in the fueltank. There it is well protected againstcorrosion and the pump noise is adequatelysoundproofed.

25 - Electric fuel pump

Index Explanation Index Explanation1 Impeller 6 Electrical connection2 Drive shaft 7 Sliding contacts3 Electric motor 8 Pressure chamber4 Pressure relief valve 9 Intake section5 Pressure connection

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The fuel pump on BMW diesel engines mayeither be a gear pump, a roller-cell pump or ascrew-spindle pump. The following fuelpumps are used on USA vehicles:

The operating principle of each of these typesof pump is described below. The pump itself isdriven by the drive shaft (2) of the electricmotor (3). The electric motor is controlled bythe electrical connection (6) and slidingcontacts (7).

Passing first through the intake filter and thenthe remainder of the intake section (9), the fuelenters the impeller (1). The fuel is pumpedthrough pressure chamber (8) on the electricmotor, past the pressure connection (5) andonwards to the fuel filter and engine.

If the fuel delivery pressure increases to animpermissible value, the pressure relief valve(4) opens and allows the fuel to flow into thesurge chamber.

Control

In principle, there are three different types offuel pump control:

• Unregulated:The fuel pump operates with "ignition ON".If the engine is not started, the fuel pumpswitches off again after a defined period. Ifthe engine is running, the fuel pump

operates at maximum output and speed.The fuel is switched off with "engine OFF".

• Speed-regulated:The fuel pump operates with "ignition ON".If the engine is not started, the fuel pumpswitches off again after a defined period.The fuel pump is controlled by aninterposed control unit (fuel pumpcontroller) in response to a request signalfrom the DDE. The fuel pump controllermonitors and regulates the pump speed. Ifthe engine is switched off, so too is the fuelpump.

• Pressure-regulated:The fuel pump operates with "ignition ON".If the engine is not started, the fuel isswitched off at a specific pressure. Whenthe engine is running, the fuel pump isregulated on-demand by the interposedfuel pump controller in response to a loadsignal from the DDE in order to ensure auniform fuel pressure at the inlet to thehigh-pressure pump.

Both speed regulation and pressure regulationhave improved fuel economy, although it hasbeen possible to improve fuel economyfurther still with pressure regulation. Otherpositive side effects include an increase in thefuel pump's service life, an unloading of thevehicle electrical system and a reduction infuel pump noise.

Vehicle Fuel pumpE70 Screw-spindle pumpE90 Gear pump

Vehicle ControlE70 Pressure controlE90 Speed control

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Gear pump

The type of gear pump used is a rotor pump.

The rotor pump comprises an outer rotor (1)with teeth on the inside, and an inner rotor (4)with teeth on the outside. The inner rotor isdriven by the drive shaft (5) of the electricmotor. The outer rotor is propelled by theteeth of the inner rotor and thus turns insidethe pump housing.

The inner rotor has one tooth fewer than theouter rotor, which means that, with eachrevolution, fuel is carried into the next toothgap of the outer rotor.

During the rotary motion, the spaces on theintake side enlarge, while those on thepressure side become proportionately smaller.

The fuel is fed into the rotor pump through twogrooves in the housing, one on the intake sideand one on the pressure side. Together withthe tooth gaps, these grooves form the intakesection (6) and pressure section (3).

26 - Gear pump/rotor pump

Index Explanation1 Outer rotor2 Fuel delivery to the engine3 Pressure section4 Inner rotor5 Drive shaft6 Intake section7 Fuel from the fuel tank

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Screw-spindle pump

With the screw-spindle pump, two screwspindles intermesh in such a way that theflanks form a seal with each other and thehousing. In the displacement chambersbetween the housing and the spindles, thefuel is pushed towards the pressure side withpractically no pulsation.

In this way, the screw spindles pump fuel awayfrom the fuel tank (5). The fuel is then fed tothe engine (3) through the pump housing andthe fuel delivery line.

27 - Screw-spindle pump

Index Explanation1 Drive shaft screw spindle2 Gearwheel3 Fuel delivery to the engine4 Screw spindle5 Fuel from the fuel tank

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Fuel filterThe fuel filter with heater illustrated here wasused in vehicle models with diesel engine anddistributor injection pump. Later models withdiesel engine and common rail system areequipped with the following fuel filters.

3 BMW recommends the use of parts andaccessories for the vehicle that have beenapproved by BMW for this purpose. Theseparts and accessories have been tested byBMW for their functional safety andcompatibility in BMW vehicles. BMW acceptsproduct responsibility for them. However,BMW cannot accept any liability for non-approved parts or accessories. 1

The job of the fuel filter is to protect the fuelsystem against dirt contamination. The high-pressure pump and injectors in particular arevery sensitive and can be damaged by eventhe tiniest amounts of dirt. The fuel deliveredto the engine is always fed through the fuelfilter. Contaminants are trapped by a paper-like material. The fuel filter is subject to areplacement interval.

28 - Fuel filter with heater (later vehicle models)

Index Explanation1 Fuel filter heater connection2 Inlet into the fuel filter heating3 Locking clamp4 Fuel filter5 Connection between fuel line and

high-pressure pump

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Fuel filter heaterThe fuel filter heater is attached to the fuelfilter housing and fixed with a locking clamp.The fuel flows through the fuel filter heatinginto the fuel filter.

Since winter-grade diesel fuel remains thineven at low temperatures, the fuel filter heateris not normally active when winter-gradediesel fuel is used. In order to save energy, thefuel filter heater is only switched on when thediesel actually becomes viscous due to lowtemperatures.

There are two different control systemsdepending on whether the fuel supply systemis speed-controlled or pressure-controlled.

Speed-controlled system

The fuel filter heater is not controlled by theDDE. A pressure switch and a temperaturesensor are located in the fuel filter housing.

The fuel filter heater is switched on when bothof the following conditions are fulfilled:

• Temperature drops below a defined value

• A defined fuel delivery pressure isexceeded due to cold, viscous fuel.

If the filter is clogged, a corresponding signal issent via a diagnosis line to the DDE. This is thecase when, despite a sufficiently hightemperature, the fuel pressure upstream ofthe filter does not drop.

Pressure-controlled system

The fuel filter heater is actuated by the DDE. Acombined fuel pressure and temperaturesensor upstream of the high pressure pump isused.

The fuel filter heater is switched on when bothof the following conditions are fulfilled:

• Temperature drops below a defined value

• The required fuel pressure is not reacheddespite increased power intake of theelectric fuel pump.

The DDE recognizes a clogged filter when thetarget pressure upstream of the high pressurepump is not reached despite a sufficiently highfuel temperature and high power intake of theelectric fuel pump.

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Overview of selective catalytic reduction

Selective catalytic reduction is a system forreducing nitrogen oxides (NOx) in the exhaustgas. For this purpose, a reducing agent (urea-water solution) is injected into exhaust gasdownstream of the diesel particulate filter.

The nitrogen oxide reduction reaction thentakes place in the SCR catalytic converter.

The urea-water solution is carried in tworeservoirs in the vehicle. The quantity ismeasured out such that it is sufficient for oneoil change interval.

The following graphic shows a simplifiedrepresentation of the system:

29 - Simplified representation of SCR system

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The reason for using two reservoirs is that theurea-water solution freezes at a temperatureof -11 °C. For this reason, the smaller reservoiris heated but the larger reservoir not. In thisway, the entire volume of the urea-watersolution need not be heated, thus savingenergy. The amount is sufficient, however, tocover large distances.

The small, heated reservoir is referred to asthe active reservoir. A pump conveys the urea-water solution from this reservoir to themetering module. This line is also heated.

The larger, unheated reservoir is the passivereservoir. A pump regularly transfers the urea-water solution from the passive reservoir tothe active reservoir.

Index Explanation Index Explanation1 Passive reservoir 10 Pump2 Level sensors 11 Filter3 Filler pipe, passive reservoir 12 Transfer line4 Metering line 13 Metering module5 Metering line heater 14 Level sensor6 Pump 15 Filler pipe, active reservoir7 Function unit 16 Exhaust system8 Heater in active reservoir 17 SCR catalytic converter9 Active reservoir

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Installation locations in the E70

30 - Installations locations, E70 SCR system

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On the E70, the active reservoir, including thedelivery unit, is located on the right-hand sidedirectly behind the front bumper panel. Thepassive reservoir is located on the left in the

underbody, approximately under the driver'sseat. The transfer unit is installed on the rightin the underbody. Both fillers are located in theengine compartment.

Index Explanation Index Explanation1 Active reservoir 8 Passive reservoir2 Delivery module 9 Metering module3 Filler for active reservoir 10 Exhaust gas temperature sensor

after diesel particulate filter4 Transfer unit 11 NOx sensor before SCR catalytic

converter5 Filter 12 Filler for passive reservoir6 SCR catalytic converter 13 Oxidation catalytic converter and

diesel particulate filter7 NOx sensor after SCR catalytic

converter

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Installation locations in the E90

31 - Installations locations, E90 SCR system

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On the E90, both the active reservoir as well asthe passive reservoir are located under theluggage compartment floor with the activereservoir being the lowermost of both. Thefillers are located on the left-hand side behindthe rear wheel where they are accessible

through an opening in the bumper panel. Thefillers are arranged in the same way as thereservoirs, i.e. the lowermost is the filler for theactive reservoir. The transfer unit and the filterare located behind the filler.

Index Explanation Index Explanation1 Active reservoir 8 Passive reservoir2 Delivery module 9 Metering module3 Filler for active reservoir 10 Exhaust gas temperature sensor

after diesel particulate filter4 Transfer unit 11 NOx sensor before SCR catalytic

converter5 Filter 12 Filler for passive reservoir6 SCR catalytic converter 13 Oxidation catalytic converter and

diesel particulate filter7 NOx sensor after SCR catalytic

converter

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Detailed system overview

32 - SCR system overview

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Index Explanation Index Explanation1 Operating vent 19 Filter2 Passive reservoir 20 Metering line heater3 Level sensors 21 Metering line4 Filler vent 22 Operating vent5 Filler pipe 23 Temperature sensor6 Transfer line 24 Level sensor7 Delivery module 25 Intake line heater8 Delivery module heater 26 Filter9 Delivery pump 27 Active reservoir10 Reversing valve 28 Heating element in function unit11 Filter 29 Function unit12 Pressure sensor 30 Filler pipe13 Filter 31 Metering module14 Restrictor 32 NOx sensor before SCR catalytic

converter15 Extractor connections 33 Exhaust gas temperature sensor

after diesel particulate filter16 Filler vent 34 SCR catalytic converter17 Non-return valve 35 NOx sensor after SCR catalytic

converter18 Transfer pump

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E70 System circuit diagram

33 - E70 SCR system circuit diagram

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Index Explanation Index Explanation1 Heater module 10 Exhaust gas temperature sensor

after diesel particulate filter2 Delivery module with delivery pump,

reversing valve, pressure sensor andheater

11 Transfer pump

3 Function unit with level sensor inactive reservoir, temperature sensorand heater

12 Power distributor, battery

4 Active reservoir 13 Passive reservoir5 Metering line heater 14 Level sensors in passive reservoir6 Digital Diesel Electronics (DDE) 15 Evaluator, level sensors in passive

reservoir7 NOx sensor after SCR catalytic

converter16 DDE main relay

8 NOx sensor before SCR catalyticconverter

17 Power distributor, junction box

9 Metering module 18 Evaluator, level sensor in activereservoir

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E90 System circuit diagram

34 - E90 SCR system circuit diagram

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Index Explanation Index Explanation1 DDE main relay 11 Transfer pump2 Digital Diesel Electronics (DDE) 12 Evaluator, level sensor in active

reservoir3 SCR relay 13 Function unit with level sensor in

active reservoir, temperature sensorand heater

4 Power distributor, junction box 14 Active reservoir5 Exhaust gas temperature sensor

after diesel particulate filter15 Delivery module with delivery pump,

reversing valve, pressure sensor andheater

6 Metering module 16 Heater module7 Power distributor, battery 17 NOx sensor after SCR catalytic

converter8 Passive reservoir 18 NOx sensor before SCR catalytic

converter9 Level sensors in passive reservoir 19 SCR load relay10 Evaluator, level sensors in passive

reservoir20 Metering line heater

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Functions of selective catalytic reduction system

Selective catalytic reduction is currently themost effective system for reducing nitrogenoxides (NOx). During operation, it achieves anefficiency of almost 100 % and approx. 90 %over the entire vehicle operating range. Thedifference is attributed to the time the system

requires until it is fully operative after a coldstart.

This system carries a reducing agent, urea-water solution, in the vehicle.

The urea-water solution is injected into theexhaust pipe by the metering moduleupstream of the SCR catalytic converter. TheDDE calculates the quantity that needs to beinjected. The nitrogen oxide content in theexhaust gas is determined by the NOx sensorbefore the SCR catalytic converter.Corresponding to this value, the exact quantityof the urea-water solution required to fullyreduce the nitrogen oxides is injected.

The urea-water solution converts to ammoniain the exhaust pipe. In the SCR catalyticconverter, the ammonia reacts with the

nitrogen oxides to produce nitrogen (N2) andwater (H2O).

A further NOx sensor that monitors thisfunction is located downstream of the SCRcatalytic converter.

A temperature sensor in the exhaust pipe afterthe diesel particulate filter (i.e. before the SCRcatalytic converter) and the metering modulealso influences this function. This is becauseinjection of the urea-water solution onlybegins at a minimum temperature of 200 °C.

35 - SCR functions

Index Explanation Index Explanation1 NOx sensor before SCR catalytic

converter3 NOx sensor after SCR catalytic

converter2 Metering module 4 Temperature sensor after diesel

particulate filter

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Chemical reactionThe task of the SCR system is to substantiallyreduce the nitrogen oxides (NOx) in theexhaust gas. Nitrogen oxides occur in twodifferent forms:

• Nitrogen monoxide (NO)

• Nitrogen dioxide (NO2).

Ammonia (NH3) is used for the purpose ofreducing the nitrogen oxides in a specialcatalytic converter.

The ammonia is supplied in the form of a urea-water solution.

The urea-water solution is injected by themetering system into the exhaust systemdownstream of the diesel particulate filter. Therequired quantity must be metered exactly asotherwise nitrogen oxides or ammonia wouldemerge at the end. The following descriptionof the chemical processes explains why this isthe case.

Conversion of the urea-water solution

The uniform distribution of the urea-watersolution in the exhaust gas and the conversionto ammonia take place in the exhaust pipeupstream of the SCR catalytic converter.

Initially, the urea ((NH2)2CO) dissolved in theurea-water solution is released.

The conversion of urea into ammonia takesplace in two stages.

36 - Nitrogen oxides

37 - Ammonia

38 - Urea-water solution

39 - Release of urea from theurea-water solution

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This means, only a part of the urea-watersolution is converted into ammonia duringthermolysis. The remainder, which is in the

form of isocyanic acid, is converted in asecond step.

The water required for this purpose is alsoprovided by the urea-water solution.

Therefore, following hydrolysis, all the urea isconverted into ammonia and carbon dioxide.

ThermolysisExplanation: During thermolysis, the urea-water solution is split into two products

as the result of heating.Initial product: Urea ((NH2)2CO)Result: Ammonia (NH3)

Isocyanic acid (HNCO)Chemical formula: (NH2)2CO → NH3 + HNCO

40 - Thermolysis: Urea converts to ammonia and isocyanic acid

HydrolysisExplanation: The isocyanic acid that was produced during thermolysis is converted

into ammonia and carbon dioxide (CO2) by the addition of water in thehydrolysis process.

Initial products: Isocyanic acid (HNCO)

Water (H2O)Result: Ammonia (NH3)

Carbon dioxide (CO2)Chemical formula: HNCO + H2O → NH3 + CO2

41 - Hydrolysis: Isocyanic acid reacts with water to form ammonia and carbon dioxide

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NOx reduction

Nitrogen oxides are converted into harmlessnitrogen and water in the SCR catalyticconverter.

It can be seen that each individual atom hasfound its place again at the end of the process,i.e. exactly the same elements are on the leftas on the right. This takes place only when theratio of the urea-water solution to nitrogenoxides is correct. Nitrogen oxides would

emerge if too little urea-water solution wereinjected. By the same token, ammonia wouldemerge if too much urea-water solution wereinjected, resulting in unpleasant odour andpossible damage to the environment.

42 - Nitrogen and water

ReductionExplanation: The catalytic converter serves as a "docking" mechanism for the

ammonia molecules. The nitrogen oxide molecules meet theammonia molecules and the reaction starts and energy is released.This applies to NO in the same way as to NO2.

Initial products: Ammonia (NH3)

Nitrogen monoxide (NO)

Nitrogen dioxide (NO2)

Oxygen (O2)Result: Nitrogen (N2)

Water (H2O)Chemical formulae: NO + NO2 + 2NH3 → 2N2 + 3H2O

4NO + O2 + 4NH3 → 4N2 + 6H2O

6NO2 + 8NH3 → 7N2 + 12H2O

43 - NOx reduction: Nitrogen oxides react with ammonia to form nitrogen and water

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SCR controlThe SCR control is integrated in the digitaldiesel electronics (DDE). The SCR control is

divided into the metering system control andthe metering strategy.

44 -

Index Explanation Index Explanation1 Digital diesel electronics DDE7 10 Pressure sensor2 SCR control 11 Temperature sensor in active

reservoir3 Metering system control 12 Outside temperature sensor4 Metering strategy 13 Level sensor in active reservoir5 Injection pump 14 Level sensor in passive reservoir6 Transfer pump 15 NOx sensor before SCR catalytic

converter7 Metering module 16 NOx sensor after SCR catalytic

converter8 Heater 17 Exhaust temperature sensor9 Reversing valve

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Metering strategy

The metering strategy is an integral part of theSCR control that calculates how much area-water solution is to be injected at what time.

During normal operation, the signal from theNOx sensor before the SCR catalyticconverter is used for the purpose ofcalculating the quantity. This sensordetermines the quantity of nitrogen oxide inthe exhaust gas and sends the correspondingvalue to the DDE.

However, the NOx sensor must reach itsoperating temperature before it can startmeasuring. Depending on the temperature,this can take up to 15 minutes. Until then theDDE uses a substitute value to determine theamount of nitrogen oxide in the exhaust gas.

A second NOx sensor is installed after theSCR catalytic converter for the purpose ofmonitoring the system. It measures whetherthere are still nitrogen oxides in the exhaustgas. If so the injected quantity of the urea-water solution is correspondingly adapted.The NOx sensor, however, measures not onlynitrogen oxides but also ammonia but cannotdistinguish between them.

If too much urea-water solution is injected,although the nitrogen oxides are completelyreduced so-called "ammonia slip" occurs, i.e.ammonia emerges from the SCR catalyticconverter. This in turn causes a rise in thevalue measured by the NOx sensor. The aim,

therefore, is to achieve a minimum of thesensor value.

This, however, is a long-term adaptation andnot a short-term control process as the SCRcatalytic converter performs a storage functionfor ammonia.

45 - Nitrogen and ammonia emission diagram

Index ExplanationA Value output by NOx sensorB Injected quantity of urea-water

solution1 Too little urea-water solution

injected2 Correct quantity of little urea-water

solution injected3 Too much urea-water solution

injected

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Metering system control

The metering system control could beconsidered as the executing part. It carries outthe requirements set by the metering strategy.This includes both the metering, i.e. injectionas well as the supply of the urea-watersolution.

The tasks of the metering system controlduring normal operation are listed in thefollowing:

Metering of the urea-water solution:

• Implementation of the required targetquantity of urea-water solution

• Feedback of the implemented actualquantity of urea-water solution.

Supplying urea-water solution:

• Preparation of metering process (filling linesand pressure built-up) under correspondingambient conditions (temperature)

• Emptying lines during afterrunning

• Heater actuation.

In addition, the metering system controlrecognizes faults, implausible conditions orcritical situations and initiates correspondingmeasures.

Metering of the urea-water solutionThe metering strategy determines thequantity of urea-water solution to be injected.The metering system control executes thisrequest. A part of the function is meteringactuation that determines the actual openingof the metering valve.

Depending on the engine load, the meteringvalve injects at a rate of 0.5 Hz to 3.3 Hz.

The metering actuation facility calculates thefollowing factors in order to inject the correctquantity:

• The duty factor of the actuator of themetering valve in order to determine theinjection duration

• Actuation delay to compensate for thesluggishness of the metering valve.

The signal from the pressure sensor in themetering line is taken into account to ensurean accurate calculation; the pressure,however, should remain at a constant 5 bar.

The metering system control also calculatesthe quantity actually metered and signals thisvalue back to the metering strategy.

The metering quantity is also determined overa longer period of time. This long-termcalculation is reset during refuelling or can bereset by the BMW diagnosis system.

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Supplying urea-water solutionA supply of a urea-water solution is requiredfor the selective catalytic reduction process. Itis necessary to store this medium in thevehicle and to make it available rapidly underall operating conditions. In this case 'makingavailable' means that the urea-water solutionis applied at a defined pressure at themetering valve.

Various functions that are described in thefollowing are required to carry out this task.

Heater

The system must be heated as the urea-watersolution freezes at a temperature of -11 °C.

The heating system performs following tasks:

• To monitor the temperature in the activereservoir and the ambient temperature

• To thaw a sufficient quantity of urea-watersolution and the components required formetering the solution during system start-up

• To prevent the relevant componentsfreezing during operation

• To monitor the components of the heatingsystem.

The following components are heated:

• Surge chamber in active reservoir

• Intake line in active reservoir

• Delivery module (pump, filter, reversingvalve)

• Metering line (from active reservoir tometering module).

The heating systems for the metering line anddelivery module are controlled dependent onthe ambient temperature.

The heater in the active reservoir is controlledas a function of the temperature in the activereservoir.

The heating control is additionally governed bythe following conditions:

Temperature in active reservoir and ambient temperature are the sameCondition 1 Condition 2 Condition 3 Condition 4

Ambient temperature andtemperature in active reservoir

> -4 °C < -4 °C < -5 °C < -9 °C

Metering line heater Not active Not active Active ActiveActive reservoir heater Not active Active Active ActiveMetering standby Established Established Established Delayed

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Metering standby is delayed at a temperaturebelow -9 °C in the active reservoir, i.e. adefined waiting period is allowed to elapseuntil an attempt to build up pressure begins.This time is constant from -9 °C to -16.5 °C asit is not possible to determine to what extentthe urea-water solution is frozen. Attemperatures below -16.5 °C, the heatingtime is extended until an attempt to build upthe pressure is made.

Heating the metering line generally takesplace much faster. Therefore, the temperature

in the active reservoir is the decisive factor forthe period of time until an attempt to build upthe pressure is undertaken. However, it ispossible that the heating time for the meteringline is longer at ambient temperatureconsiderably lower than the temperature in theactive reservoir. In this case, the ambienttemperature is taken for the delay in meteringstandby.

The following graphic shows the delay as afunction of the temperature sensor signals.

The graphic shows that, with the sametemperature signals, the delay time relating tothe temperature in the active reservoir islonger than the delay caused by the ambienttemperature.

Only the times at temperatures below -9 °Care relevant as they are shorter than 3 minutesat temperatures above -9 °C. 3 minutes is thetime that the entire system requires toestablish metering standby (e.g. also taking

into account the temperature in the SCRcatalytic converter). This is also the time that isapproved by the EPA (EnvironmentalProtection Agency) as the preliminary periodunder all operating conditions. This time isextended significantly at very lowtemperatures.

The following example shows how the delaytime up to metering standby is derived at lowtemperatures.

46 - Diagram - meteringstandby delay times

Index Explanation Index ExplanationA Delay as a function of temperature in

active reservoirB Delay as a function of ambient

temperaturet [s] Delay time in seconds T [°C] Temperature in degrees Celsius

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Example: Ambient temperature: -30 °C,temperature in active reservoir: -12 °C

The vehicle was driven for a longer period oftime at very low ambient temperatures of -30 °C. The heater in the active reservoir hasthawed the urea-water solution. The vehicle isnow parked for a short period of time (e.g. 30minutes). When restarted, the temperature inthe active reservoir is -12 °C.

The delay time that is initiated by thetemperature in the active reservoir is approx.18 minutes while the delay time initiated bythe ambient temperature is 25 minutes. Sincethe delay time initiated by the ambienttemperature is longer, this will give rise to alonger delay.

Now another condition comes into play. Onlythe end of the delay caused by the

temperature in the active reservoir can enablemetering. This means:

• The delay time initiated by the temperaturein the active reservoir will have elapsed after18 minutes. No enable is yet provided bythe second delay caused by the ambienttemperature. A second cycle of 18 minutesnow begins.

• The delay time initiated by the ambienttemperature will elapse after 25 minutesand will send its enable signal. However,this delay cannot enable metering.

• The second cycle of the delay time causedby the temperature in the active reservoirwill have elapsed after 36 minutes. Sincethe enable from the delay caused by theambient temperature is now applied,metering will be enabled.

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Transfer pumping

So-called transfer pumping is required sincetwo reservoirs are used for storing the urea-water solution. The term transfer pumping

relates to pumping the urea-water solutionfrom the passive reservoir into the activereservoir.

The following conditions must be met fortransfer pumping:

• There is a urea-water solution in the passivereservoir

• The ambient temperature is above aminimum value of -5 °C for at least 10minutes

• A defined quantity (300 ml) was used up inthe active reservoir or the reserve level inthe active reservoir was reached.

The solution is then pumped for a certain timein order to refill the active reservoir. Thetransfer pumping procedure is terminated ifthe "full" level is reached before the time haselapsed.

If the passive reservoir was refilled, transferpumping will only take place after a quantity ofapprox. 3 l has been used up in the activereservoir. The entire quantity is then pumpedover. The system then waits again until aquantity of approx. 3 l has been used up in theactive reservoir before again pumping theentire quantity while simultaneously startingthe incorrect refilling detection function. Thisfunction determines whether the system hasbeen filled with the wrong medium as it ispresent in high concentration in the activereservoir.

Transfer pumping does not take place in theevent of a fault in the level sensor system.

47 - Transfer pumping

Index Explanation Index Explanation1 Passive reservoir 6 Pump2 Level sensors 7 Non-return valve3 Extractor connections 8 Level sensor4 Transfer line 9 Active reservoir5 Filter

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Delivery

The urea-water solution is delivered from theactive reservoir to the metering module. Thistask is performed by a pump that is integratedin the delivery unit. The delivery unitadditionally contains:

• Heater

• Pressure sensor

• Filter

• Return throttle

• Reversing valve.

The pump is actuated by a pulse-widthmodulated signal (PWM signal) from the DDE.The PWM signal provides a speedspecification for the purpose of establishingthe system pressure. The value for the speedspecification is calculated by the DDE basedon the signal from the pressure sensor.

When the system starts up, the pump isactuated with a defined PWM signal and theline to the metering module is filled. This isfollowed by pressure build-up. Only then doespressure control take place.

48 - Delivery

Index Explanation Index Explanation1 Metering line 8 Filter2 Delivery module 9 Level sensor3 Pump 10 Filter4 Reversing valve 11 SCR catalytic converter5 Filter 12 Exhaust system6 Restrictor 13 Metering module7 Pressure sensor

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When the metering line is filled, the openedmetering valve allows a small quantity of theurea-water solution to be injected into theexhaust system.

During pressure control, i.e. during normaloperation with metering, the pump is actuatedin such a way that a pressure of 5 bar is appliedin the metering line. Only a small part of theurea-water solution delivered by the pump isactually injected. The majority of the solution istransferred via a throttle back into the activereservoir. This means, the delivery pressure isdetermined by the pump speed together withthe throttle cross section.

The solution is injected four times per second.The quantity is determined by the openingtime and stroke of the metering valve.However, the quantity is so low that there is nonoticeable drop in pressure in the meteringline.

Evacuating

After turning off the engine, the reversing valveswitches to reverse the delivery direction ofthe pump, thus evacuating the metering lineand metering module.

49 - Evacuating

Index Explanation Index Explanation1 Metering line 8 Filter2 Delivery module 9 Level sensor3 Pump 10 Filter4 Reversing valve 11 SCR catalytic converter5 Filter 12 Exhaust system6 Throttle 13 Metering module7 Pressure sensor

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Evacuation also takes place if the system hasto be shut down due to a fault or if theminimum temperature in the active reservoircan no longer be maintained.

This is necessary to ensure no urea-watersolution remains in the metering line ormetering module as it can freeze.

The metering valve is opened duringevacuation.

Level measurement

There are level sensors both in the active aswell as in the passive reservoir. However,these sensors are not continuous sensors asin the fuel system for example. They candetermine only a specific point, to which adefined quantity of urea-water solution in thereservoir is assigned.

Two separate level sensors are fitted in thepassive reservoir, one for "full" and one for"empty". The signals from the level sensorsare not sent directly to the DDE but rather toan evaluator.

The active reservoir contains one level sensorthat has various measuring points:

• Full

• Warning

• Empty.

Also in this case, there is an evaluator installedbetween the sensors and the DDE, whichfulfils the same tasks as for the passivereservoir.

This evaluator sends a plausible level signal tothe DDE. It recognizes changes in the fill levelcaused, for example, by driving uphill/downhillor sloshing of the liquid as opposed to anactual change in the liquid level in thereservoir. Low level is therefore signalled whenthe corresponding sensor is no longer coveredby the urea-water solution for a defined periodof time. Once the level drops below this value,it can no longer be reached during normaloperation. This means, the liquid sloshing onthe sensor or driving uphill/downhill is nolonger interpreted as a higher liquid level.

50 - Example: Level signal OK

Index Explanation1 Measuring point "Full"2 Measuring point "Warning"3 Measuring point "Empty"4 Reference5 Level

Level of urea-water solution Level signalLevel > Full FullFull > Level > Warning OKWarning > Level > Empty WarningEmpty > Level Empty

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The level measurement system must alsorecognize when the active and passivereservoirs are refilled. This is achieved bycomparing the current level with the value laststored.

The level sensor signal after refillingcorresponds to the signal while driving uphill.To avoid possible confusion, the refillingrecognition function is limited to a certainperiod of time after starting the engine anddriving off - as it can be assumed that refillingwill only take place while the vehicle isstationary.

A certain vehicle speed must be exceeded toensure that sloshing occurs, thus providing aclear indication that the system has beenrefilled.

Refilling the system while the engine isrunning can also be detected but withmodified logic. The signals sent by thesensors while the vehicle is stationary are alsoused for this purpose. The vehicle must bestationary for a defined minimum period inorder to make the filling plausible.

When the urea-water solution is frozen, a levelsensor will show the same value as when it isnot wetted/covered by the solution. A frozenreservoir is therefore shown as empty. For thisreason, the following sensor signals are usedfor measuring the level:

• Ambient temperature

• Temperature in active reservoir

• Heater enable.

Level calculation

This function calculates the quantity of urea-water solution remaining in the active

reservoir. The calculation is calibratedtogether with the level measurement.

Every time the level drops below a level sensorthe corresponding amount of urea-watersolution in the reservoir is stored. The amountof urea-water solution actually injected is thensubtracted from this value while the pumpedquantity is added.

This makes it possible to determine the levelmore precisely than that would be possible bysimple measurement. In addition, the level canstill be determined in the event of one of thelevel sensors failing.

Since it is possible that refilling is notrecognized, the calculation is continued onlyuntil the level ought to drop below the nextlower sensor.

Example:

Once the level drops below the "full" levelsensor, for example, from now on the quantityof used and repumped urea-water solution istaken into account and the actual level below"full" calculated. Normally, the level then dropsbelow the next lower level sensor at the sametime as determined by the level calculation. Anadjustment takes place at this point and thecalculation is restarted.

If, however, a quantity of urea-water solution isrefilled without it being detected, the actuallevel will be higher than the calculated level.The level calculation is stopped if it calculatesthat the level ought to have dropped below thenext level sensor but the level sensor is stillwetted/covered.

By way of exception, a defective level sensorcan cause the calculation to continue until thereservoir is empty.

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SCR system modesWhen the ignition is switched on, the SCRcontrol undergoes a logical sequence ofmodes in the DDE. There are conditions thatinitiate the change from one mode to the

other. The following graphic shows thesequence of modes which are subsequentlydescribed.

51 - Sequence of modes in SCR control

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INIT (SCR initialization)

The control unit is switched on (terminal 15ON) and the SCR system is initialized.

STANDBY (SCR not active)

STANDBY mode is assumed either afterinitialization or in the case of fault.

AFTERRUN mode is assumed if terminal 15 isswitched off in this state or a fault occurs.

NOPRESSURECONTROL (waiting forenable for pressure control)

NOPRESSURECONTROL mode is assumedwhen no faults occur in the system. In thismode, the system is waiting for the pressurecontrol enable that is provided by the followingsensor signals:

• Temperature in catalytic converter

• Temperature in active reservoir

• Ambient temperature

• Engine status (engine running).

The system also remains inNOPRESSURECONTROL mode for aminimum period of time so that a plausibilitycheck of the pressure sensor can beperformed.

PRESSURECONTROL mode is assumedonce the enable is finally given.

STANDBY mode is assumed if terminal 15 isswitched off or a fault occurs inNOPRESSURECONTROL mode.

PRESSURECONTROL (SCR systemrunning)

PRESSURECONTROL mode is the normaloperating status of the SCR system and hasfour submodes.

PRESSURECONTROL mode is maintaineduntil terminal 15 is switched off. A change toPRESSUREREDUCTION mode then takesplace.

A change to PRESSUREREDUCTION modealso takes place if a fault occurs in the system.

The four submodes ofPRESSURECONTROL are described in thefollowing:

• REFILL

The delivery module, metering line and themetering module are filled when REFILLmode is assumed. The pump is actuatedand the metering valve opened by a definedvalue. The fill level is calculated.

The mode changes toPRESSUREBUILDUP when the required filllevel is reached or a defined pressureincrease is detected.

PRESSUREREDUCTION mode isassumed if terminal 15 is switched off or afault occurs in the system.

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• PRESSUREBUILDUP

In this mode, the pressure is built up to acertain value. For this purpose, the pump isactuated while the metering valve is closed.

If the pressure is built up within a certaintime, the system switches to the next modeof METERINGCONTROL. If the requiredpressure built-up is not achieved after thedefined period of time has elapsed, a statusloop is initiated, and VENTILATION mode isassumed.

If the pressure cannot be built up after adefined number of attempts, the systemsignals a fault and assumesPRESSUREREDUCTION mode.

PRESSUREREDUCTION mode is alsoassumed when terminal 15 is switched offor another fault occurs in the system.

• VENTILATION

If the pressure could not be increasedbeyond a certain value inPRESSUREBUILDUP mode, it is assumedthat there is still air in the pressure line.

The metering valve is opened for a definedperiod of time to allow this air to escape.This status is exited after this time haselapsed and the system returns toPRESSUREBUILDUP mode. The loop

between PRESSUREBUILDUP andVENTILATION varies corresponding to thecondition of the reducing agent. The reasonfor this is that a different level is establishedafter REFILL depending on the ambientconditions. Repeating the ventilationfunction will ensure that the pressure line iscompletely filled with reducing agent.

PRESSUREREDUCTION mode isassumed if terminal 15 is switched off or afault occurs in the system.

• METERINGCONTROL

The system can enable metering inMETERINGCONTROL mode. This is theactual status during normal operation. Theurea-water solution is injected in this mode.

In this mode, the pump is actuated in sucha way that a defined pressure is established.This pressure is monitored. If the pressureprogression overshoots or undershootsdefined parameters, a fault is detected andthe system assumesPRESSUREREDUCTION mode. Thesefaults are reset on return toMETERINGCONTROL mode.

PRESSUREREDUCTION mode is alsoassumed if terminal 15 is switched off oranother fault occurs in the system.

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PRESSUREREDUCTION

Metering enable is cancelled on enteringPRESSUREREDUCTION mode.

This status reduces the pressure in thedelivery module, metering line and themetering module afterPRESSURECONTROL mode. For thispurpose, the reversing valve is opened and thepump actuated at a certain value, the meteringvalve is closed.

PRESSUREREDUCTION mode ends whenthe pressure drops below a certain value. Thesystem assumes NOPRESSURECONTROLmode if the pressure threshold is reached(undershot) within a defined time.

The system signals a fault if the pressure doesnot drop below the threshold after a definedtime has elapsed. In this case or also in thecase of another fault, the system assumesNOPRESSURECONTROL mode.

NOPRESSURECONTROL mode is alsoassumed when terminal 15 is switched on.

AFTERRUN

The system is shut down in AFTERRUNmode.

If terminal 15 is switched on again beforeafterrun has been completed, afterrun iscancelled and STANDBY mode is assumed. Ifthis is not the case the system goes throughthe submodes of AFTERRUN.

• TEMPWAIT (catalytic convertercooling phase)

In AFTERRUN mode, TEMPWAITsubmode is initially assumed if the systemis filled. This is intended to preventexcessively hot exhaust gasses beingdrawn into the SCR system.

The duration of the cooling phase isdetermined by the exhaust gastemperature. EMPTYING submode isassumed after this time, in which theexhaust system cools down, has elapsed.

EMPTYING submode is also assumed if afault occurs in the system.

If terminal 15 is switched on in this status,STANDBY mode is assumed.

• EMPTYING

The system assumesAFTERRUN_EMPTYING submode afterthe cooling phase. The pressure line andthe delivery module are emptied in thissubmode. The urea-water solution is drawnback into the active reservoir by openingthe reversing valve, actuating the pump andopening the metering valve. This isintended to prevent the urea-water solutionfreezing in the metering line or the meteringmodule.

The level in the metering line is calculated inthis mode.

PRESSURECOMPENSATION mode isassumed if the metering line is empty.PRESSURECOMPENSATION mode isalso assumed if a fault occurs in the system.If terminal 15 is switched on, STANDBYmode is assumed.

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• PRESSURECOMPENSATION (intakeline - ambient pressure)

After the system has been completelyemptied, PRESSURECOMPENSATIONsubmode is assumed. In this status thepump is switched off, the reversing valve isthen closed followed by the metering valveafter a delay. The time interval betweenswitching off the pump and closing thevalve prevents a vacuum forming in theintake line; pressure compensationbetween the intake line and ambientpressure takes place.

After executing the steps correctly thesystem assumesWAITING_FOR_SHUTOFF submode.

WAITING_FOR_SHUTOFF is alsoassumed if a fault occurs in the system.

If terminal 15 is switched on, STANDBYmode is assumed.

• WAITING_FOR_SHUTOFF (shuttingdown SCR)

The control unit is shut down and switchedoff.

Warning and shut-down scenarioThe SCR system is relevant to the vehiclecomplying with the exhaust emissionregulations - it is a prerequisite for approval/homologation! If the system fails, the approvalwill be invalidated and the vehicle must nolonger be operated. A very plausible caseleading to the system failure is that the urea-water solution runs out.

Vehicle operation is no longer permittedwithout the urea-water solution, therefore, theengine will no longer start.

To ensure the driver is not caught out, awarning and shut-down scenario is providedthat begins at a sufficiently long time beforethe vehicle actually shuts down so that thedriver can either conveniently top up the urea-water solution himself or have it topped up.

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Warning scenario

The warning scenario begins when the leveldrops below the "Warning" level sensor in theactive reservoir. At this point, the activereservoir is still approximately 50 % full withurea-water solution. The level is thendetermined as a defined volume (dependingon type of vehicle).

From this point on, the actual consumption ofthe urea-water solution is subtracted from thisvalue. The mileage is recorded when theamount of 2500 ml is reached.

A countdown from 1000 mls now takes place- irrespective of the actual consumption of theurea-water solution. The driver receives apriority 2 (yellow) check control messageshowing the remaining range.

If the vehicle is equipped with an on-boardcomputer (CID - Central Information Display),instruction will also be displayed.

The driver receives a priority 1 (red) checkcontrol message as from 200 mls.

In this case the following message is shown inthe CID:

52 - CC message in instrumentcluster, range < 1000 mls

53 - CC message in CID, range < 1000 mls

54 - CC message in instrumentcluster, range < 200 mls

55 - CC message in CID, range < 200 mls

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Shut-down scenario

If the range reaches 0 mls, similar as to in thefuel gauge, three dashes are shown instead ofthe range.

The check control message in the CIDchanges and shows that the engine can nolonger be started.

In this case, it will no longer be possible to startthe engine if it has been shut down for longerthan three minutes. This is intended to allowthe driver to move out of a hazardous situationif necessary.

If the system is refilled only after engine starthas been disabled, the logic of the refillrecognition system is changed in this specialcase, enabling faster refill.

Exhaust fluid incorrect

If the system is filled with an incorrect medium,this will become apparent after severalhundred miles (kilometres) later by elevatednitrogen oxide values in the exhaust gasdespite adequate injection of the supposedurea-water solution. The system recognizesan incorrect medium when certain limits areexceeded. From this point on, a warning andshut-down scenario is also initiated that allowsa remaining range of 200 mls.

The exclamation mark in the symbol identifiesthe fault in the system.

In this case, the message in the CID informsthe driver to go to the nearest workshop.

56 - CC message in instrumentcluster, range = 0 mls

57 - CC message in CID, range = 0 mls

58 - CC message in instrumentcluster in the case ofincorrect exhaust fluid

59 - CC message in CID in the case of incorrect exhaust fluid

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RefillingThe active and passive reservoirs can berefilled with urea-water solution either by theservice workshop or by the customer himself.

The system can be refilled without anyproblems with the vehicle on an incline of up to5° in any direction. In this case, 90 % of themaximum possible fill is still achieved.

The volume of the urea-water solutionreservoir is designed such that the range islarge enough to cover one oil change interval.This means the "normal" refill takes place aspart of the servicing work in the workshop. If,however, the supply of urea-water solutionshould run low prematurely due toextraordinary driving profile, it is possible to topup a smaller quantity.

Refilling in service workshop

Refilling in the service workshop refers to theroutine refill as part of the oil changeprocedure. This takes place at the latest after:

• 13000 mls on the E90,

• 11000 mls on the E70 or

• one year.

In this case, the system must be emptied firstin order to remove older urea-water solution.This takes place via the extractor connectionsin the transfer line. Although a small residualquantity always remains in the reservoirs, it isnegligible.

Topping up

Any required quantity can be topped up if theurea-water solution reserve does not last up tothe next oil change. Ideally, this quantityshould only be as much as is required to reachthe next oil change, as the system is thenemptied.

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Components of the selective catalytic reduction system

Urea-water solutionThe urea-water solution is the carrier for theammonia that is used to reduce the nitrogenoxides (NOx) in the exhaust gas. To protectpersons and the environment from the effectsof ammonia and to make it more easy tohandle for transport and refuelling procedures,it is provided in an aqueous urea solution forthe SCR process.

The recommended urea-water solution isAdBlue. The VDA (Association of GermanAutomobile Industry) holds the rights to thetrademark AdBlue. AdBlue is a high-purity,water-clear, synthetically manufactured32.5 % urea solution that is standardized inaccordance with DIN 70070/AUS32.

The urea-water solution used mustcorrespond to this standard.

Health and safety

The urea-water solution is not toxic. It is anaqueous solution which, according to validEuropean chemical law, poses no specialrisks. It is not a hazardous substance and it isnot a dangerous medium as defined bytransport laws.

If small amounts of the product come incontact with the skin while handling the urea-water solution it is sufficient to simply rinse itoff with ample water. In this way, the possibilityof any ill effects on human health are ruled out.

Degradability and disposal

The urea-water solution can be broken downby microbes and is therefore easilydegradable. The urea-water solution poses aminimum risk to water and soil. In Germany,the urea-water solution is categorized in thelowest water hazard class (WGK 1). In view ofits excellent degradability properties, small

quantities of spilt urea-water solution can beflushed into the sewage system with amplewater.

Materials compatibility

Contact of urea-water solution with copperand zinc as well as their alloys and aluminiummust be avoided as this leads to corrosion. Noproblems whatsoever are encountered withstainless steel and most plastics.

Storage and durability

To avoid adverse effects on quality due tocontamination and high testing expenditure,the urea-water solution should only behandled in storage and filling systemsspecifically designed for this purpose.

In view of the fact that the urea-water solutionfreezes solid at a temperature of -11 °C anddecomposes at an accelerated rate attemperatures above 25 °C, the storage andfilling systems should be set up in such a waythat a temperature range from 30 °C to -11 °Cis ensured.

Provided the recommended storagetemperature of maximum 25 °C is maintained,the urea-water solution meets therequirements stipulated by the standard DIN70070 for at least 12 months after itsmanufacture. This period of time is shortenedif the recommended storage temperature isexceeded. The urea-water solution willbecome solid if cooled to temperatures below-11 °C. When heated up, the frozen urea-water solution becomes liquid again and canbe used without any loss in quality.

Avoid direct UV radiation.

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Passive reservoirThe passive reservoir is the larger of the twosupply reservoirs.

The name passive reservoir refers to the factthat it is not heated.

The following components make up thepassive reservoir:

• Level sensors (2x)

• Operating vent (2x on E90)

• Filler vent.

Vehicle Volume Location Position of filler neckE70 16.5 l In underbody, approximately

under driver's seatOn the left in enginecompartment, under unfilteredair pipe

E90 14.4 l Under luggage compartmentfloor instead of multifunction pan

Left side in rear bumper panel

60 - E90 Passive reservoir

Index Explanation Index Explanation1 Operating vent 5 Fill line connection2 Filler vent 6 "Empty" level sensor3 "Full" level sensor 7 Passive reservoir4 Operating vent

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The passive reservoir on the E70 is encased ininsulation as it is positioned near the front ofthe exhaust system where the heat transfer tothe urea-water solution would be very high.

61 - Insulation of passive reservoir E70

62 - E70 Passive reservoir

Index Explanation Index Explanation1 Connection for transfer line 5 Fill line connection2 Operating vent 6 Filler vent3 "Full" level sensor 7 "Empty" level sensor4 Passive reservoir

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Level sensors

There are two level sensors in the passivereservoir. One supplies the "Full" signal andthe other the "Empty" signal.

The sensors make use of the conductivity ofthe urea-water solution. Two contacts projectinto the reservoir. When these contacts arewetted with urea-water solution the circuit isclosed and current can flow, thus enabling asensor signal.

The two level sensors send their signal to anevaluator. This evaluator filters the signals andrecognizes, for example, sloshing of the urea-water solution and transfers a correspondinglevel signal to the digital diesel electronics.

The "Full" level sensor is located at the top ofthe passive reservoir. Both contacts arewetted when the passive reservoir iscompletely filled and the sensor sends the"Full" signal.

The "Empty" level sensor is located at thebottom end of the passive reservoir. Thereservoir is considered to be "not empty" foras long as the sensor is covered by urea-watersolution. The evaluator detects that thepassive reservoir is empty when no sensorsignal is received.

Venting

The passive reservoir is equipped with oneoperating vent (2 in the E90) and one fillervent.

The operating vent is directed intoatmosphere. A so-called sintered tabletensures that no impurities can enter thereservoir via the operating vent. This sinteredtablet consists of a porous material and servesas a filter that allows particles only up to acertain size to pass through.

The filler vent is directed into the filler pipe andtherefore no filter is required.

63 - Level sensor in passive reservoir

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Transfer unitThe transfer unit pumps the urea-watersolution from the passive reservoir to theactive reservoir. There is a screen filter in theinlet port of the pump.

This pump is designed as a diaphragm pump.It operates in a similar way to a piston pumpbut the pump element is separated from themedium by a diaphragm. This means there areno problems regarding corrosion.

64 - Transfer unit

Index Explanation1 Connection for transfer line to

passive reservoir (inlet)2 Pump motor connection3 Connection for transfer line to

active reservoir (outlet)

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Active reservoirThe active reservoir is the smaller of the tworeservoirs and its name refers to the fact that itis heated. In view of its small volume, little

energy is required to heat the urea-watersolution.

Vehicle Volume Location Position of filler neckE70 6.4 l On front right in side panel

module between bumper paneland wheel arch

On front right in enginecompartment at the end of thesupport carrier cross member

E90 7.4 l Behind the rear axle differentialdirectly under the passivereservoir

Left side in rear bumper panel

65 - E90 Active reservoir

Index Explanation Index Explanation1 Active reservoir 4 Filler vent2 Operating vent 5 Fill line connection3 Delivery module 6 Connection of transfer line from

passive reservoir

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66 - E70 Active reservoir

Index Explanation1 Fill line connection, active reservoir2 Delivery module3 Metering line4 Filler vent5 Connection of transfer line from

passive reservoir6 Active reservoir

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Function unit

The so-called function unit is located in theactive reservoir. It has the external appearanceof a surge chamber and accommodates aheater, filter and a level sensor. The deliveryunit is attached to it.

Unlike a surge chamber in the fuel tank, thelower section of the function unit has slots.

This chamber creates a smaller volume in thereservoir that scarcely mixes with the urea-water solution outside the chamber. There is aPTC heating element (positive temperaturecoefficient) in the base of the chamber thatcan heat up this smaller volume at a relativelyfast rate. The intake line is also heated. In thisway, liquid urea-water solution can be madeavailable for vehicle operation even at thelowest temperatures.

The heating element in the chamber isconnected to the heater for the intake line toform one heating circuit. A powersemiconductor supplies the current for thisheating circuit. The power semiconductor iscontrolled by the DDE. The DDE candetermine the current that flows across theheating elements and can therefore monitortheir operation.

67 - Function unit

Index Explanation1 Operating vent2 Bowl3 Level sensor

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The temperature sensor provides the signalfor the heating control system. It is designedas an NTC sensor (negative temperaturecoefficient). The temperature sensor isintegrated at the bottom end of the levelsensor.

68 - Sectional view of functionunit

Index Explanation Index Explanation1 Level sensor 4 Intake line with heater2 Heating element 5 Operating vent3 Filter

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The level sensor in the function unit providesthe level value for the entire active reservoir.

The level sensor in the active reservoiroperates in accordance with the sameprinciple as the level sensors in the passivereservoir. In this case, however, there is onlyone sensor with several contacts that extendat different levels into the active reservoir.

The sensor makes use of the conductivity ofthe urea-water solution. A total of fourcontacts project into the reservoir. Whenthese contacts are wetted with urea-watersolution the circuit is closed and current canflow, thus enabling a sensor signal.

Three contacts are responsible for signallingthe different levels. The fourth contact is thereference, i.e. the contact via which theelectric circuit is closed. This referencecontact cannot be seen in the figure as it islocated directly behind the "Empty" contact(3).

The level sensor sends its signal to anevaluator. This evaluator filters the signal andrecognizes, for example, sloshing of the urea-water solution and transfers a correspondinglevel signal to the digital diesel electronics.

69 - Level sensor in active reservoir

Index Explanation1 "Full" contact2 "Warning" contact

3 "Empty" contactIndex Explanation

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Delivery unitThe delivery unit is located on the activereservoir at the top end of the function unit.Among other things, the delivery unitcomprises the pump that transfers the urea-water solution from the active reservoir to themetering module. The delivery unit is alsoheated by a PTC element.

The heating element in the delivery unit isconnected to the heater for the metering lineto form one heating circuit. A powersemiconductor supplies the current for thisheating circuit. The power semiconductor iscontrolled by the DDE. The DDE candetermine the current that flows across theheating elements and can therefore monitortheir operation.

Pump

The pump is a common part with the pump inthe transfer unit. While the engine is running, itpumps the urea-water solution from the activereservoir to the metering module. It sucks themetering line empty when the engine is turnedoff.

Pressure sensor

The pressure sensor measures the pressurein the delivery line to the metering module.The value is transferred to the DDE.

Reversing valve

The reversing valve ensures the deliverydirection in the metering line can be reversedto empty the metering line while the pumpdelivers in the same direction. It is designed asa 4/2-way valve interchanges the metering lineand intake line to the pump.

The valve is not actuated in intervals andtherefore has only two positions. Since poweris permanently applied to the valve when it isactuated, the maximum actuation time islimited in order to avoid overheating.

70 - Delivery unit

Index Explanation Index Explanation1 Pump motor and heater connection 3 Pressure sensor connection2 Reversing valve connection 4 Metering line connection

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Metering module and mixer

The metering module is responsible forinjecting the urea-water solution into theexhaust pipe. It features a valve that is similarto the fuel injector in a petrol engine withintake manifold injection.

Although the metering module does not havea heater, it is still heated by the exhaust system

to such an extent that it even requires coolingfins.

The metering module is actuated by a pulse-width modulated (PWM) signal from the DDEsuch that the pulse duty factor determines theopening duration of the valve.

71 - Metering module

Index Explanation Index Explanation1 Metering line connection 2 Metering valve connection

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The metering module is equipped with atapered insert (6) that prevents urea-watersolution residue drying up and clogging thevalve. Its shape creates a flow that preventsurea-water solution from collecting on thewalls of the exhaust system. Urea deposits onthe insert are burnt off as it is heated to veryhigh temperatures by the flow of exhaust gas.

Mixer

The mixer mounted in the flange connectionof the exhaust pipe is located directly behindthe metering module in the exhaust system. Itswirls the flow of exhaust gas to ensure theurea-water solution is thoroughly mixed withthe exhaust gas. This is necessary to ensurethe urea converts completely into ammonia.

72 - Metering module in installed position

Index Explanation Index Explanation1 Mixer 4 Diesel particulate filter2 NOx sensor before SCR catalytic

converter5 Metering module

3 Exhaust gas temperature sensorafter diesel particulate filter

6 Insert

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NOx sensorsThe nitrogen oxide sensor consists of theactual measuring probe and thecorresponding control unit. The control unitcommunicates via the LoCAN with the enginecontrol unit.

In terms of its operating principle, the nitrogenoxide can be compared with a broadbandoxygen sensor. The measuring principle isbased on the idea of basing the nitrogen oxidemeasurement on oxygen measurement.

The following graphic shows the functionalprinciple of this measuring system.

73 - NOx sensor

74 - Function of NOx sensor

Index Explanation Index Explanation1 Pump flow 1st chamber 5 Barrier 22 Catalytic element 6 Solid electrolyte zircon dioxide

(ZrO2)3 Nitrogen outlet 7 Barrier 14 Pump flow 2nd chamber

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The exhaust gas flows through the NOxsensor. Here, only oxygen and nitrogen oxidesare of interest. In the first chamber, the oxygenis ionized out of this mixture with the aid of thefirst pump cell and passed through the solidelectrolyte. A lambda signal can be tapped offfrom the pump current of the first chamber. Inthis way, the exhaust gas in the NOx sensor isliberated from free oxygen (not bound tonitrogen).

The remaining nitrogen oxide then passesthrough the second barrier to reach thesecond chamber of the sensor. Here, thenitrogen oxide is split by a catalytic elementinto oxygen and nitrogen. The oxygenreleased in this way is again ionized and canthen pass through the solid electrolyte. Thepump current that occurs during this processmakes it possible to deduce the quantity ofoxygen and the nitrogen level can beconcluded from this quantity.

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Engine electrical system

In contrast to the ECE version of theM57D30T2 engine, the US version of theengine electrical system features followingdifferences:

• Engine control unit DDE7

• Preheating system with LIN-bus link andceramic heater plugs

• Additional OBD sensors

• Electrically operated swirl flap and EGRvalve

• Additional actuators and sensors for the lowpressure EGR system.

Engine control unit DDE7.3The new DDE7 engine control unit that willotherwise be used in the next generation ofdiesel engines (N47, N57) is used in the USversion of the M57D30T2 engine.

The reason for this is that the capacity of theDDE6 is no longer sufficient for the additionalfunctions (especially SCR).

Preheating systemThe heating system is responsible forproviding reliable cold start properties andsmooth operation when the engine is cold.

The DDE control unit sends the temperaturerequirement of the heater plug to the heatingcontrol unit. The heating control unitimplements the request and actuates theheater plugs with a pulse-width modulatedsignal. The heating control unit additionallysends diagnosis and status information via theLIN-bus connection back to the digital dieselelectronics.

The LIN-bus is a bi-directional data interfacethat operates in accordance with the master-slave principle. The DDE control unit is themaster.

Each of the six heating circuits can bediagnosed individually.

When the heating control unit is switched onfor the first time, the electrical resistance of theheater plugs is evaluated at the start of theheating process. A hot heater plug has a muchhigher resistance than a cold plug. If hot heaterplugs are detected based on their resistance,less power is applied to the heater plugs at thestart of the heating cycle. If, on the other hand,cold heater plugs are detected, the maximumpower is applied to the heater plugs at the startof the heating cycle. This function is known asdynamic repeat heating. This function avoidsthe situation where too much power is appliedto a heater plug, which is already hot, as theresult of a second heating cycle followingshortly after the first, and therefore overheats.

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The DDE control unit determines thenecessary heater plug temperature as afunction of the following operating values:

• Engine speed

• Intake air temperature

• Injected quantity

• Ambient pressure

• System voltage

• Status signal, starter enable.

The digital diesel electronics sends therequired heater plug temperature to theheating control unit to activate heating.

The heating system assumes variousoperating modes that are explained in thefollowing.

Preheating

Preheating is activated after terminal 15 hasbeen switched on.The heater system indicator in the instrumentcluster is activated at a coolant temperature of≤ 10 °C. Preheating is finished when:

• The engine speed threshold of 42 rpm isexceeded (starter is operated)

or

• the preheating time has elapsed. Thepreheating time is dependent on thecoolant temperature and is defined in acharacteristic curve.

Start standby heating

Start standby heating is activated when thepreheating process is terminated by thepreheating time elapsing. Start standbyheating is terminated:

• After 10 seconds

or

• when the engine speed threshold of 42 rpmis exceeded.

Coolanttemperature

in °C

Preheating timein seconds

< -35 3.5-25 2.8-20 2.8-5 2.10 1.65 1.1

30 1.1> 30 0

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Start heating

Start heating is activated during every enginestart procedure when the coolant temperatureis below 75 °C. Start heating begins after theengine speed threshold of 42 rpm has beenexceeded. Start heating is terminated:

• After the maximum start heating time of 60seconds has elapsed

or

• after the engine start operation has beencompleted

or

• when the coolant temperature of 75 °C isexceeded.

Emergency heating

Emergency heating is triggered for 3 minutesin the event of communication between theDDE control unit and heating control unitfailing for more than 1 second. The heatingcontrol unit then uses safe values so as toprevent damage to the heating system.

Concealed heating

Preheating and start standby heating areactivated as so-called concealed heating up toa coolant temperature of 30 °C.

Concealed heating is triggered a maximum of4 times and is then not enabled again beforethe engine is restarted.

Concealed heating is triggered by thefollowing signals:

• Driver's seat occupancy

• Driver's seat belt buckle

• Valid key

• Terminal R

• Clutch operated.

Partial load heating

Partial load heating can occur at coolanttemperatures below 75 °C after starting theengine. Actuation of the heater plugs dependson the engine speed and load, thus improvingthe exhaust gas characteristics.

Actuation and fault detection

The power output stages for heater plugactuation are located in the heater control unit.The heater control unit does not have its ownfault code memory. Faults in the heatingsystem detected by the heater control unit aresignalled via the LIN-bus to the digital dieselelectronics. The corresponding fault codesare then stored in the DDE fault code memory.

To avoid damage, the heater control unit shutsdown all heating activities when thepermissible operating temperature of theheater control unit is exceeded.

The ceramic heater plugs are designed for anoperating voltage of 7.0 to 10.0 V. A voltage of10 V can be applied to heat up the plug at afaster rate during the heating process. A PWMsignal is applied to the heater plugs for thepurpose of maintaining the heater plugtemperature. Consequently, an effectivevoltage is established at the heater plugs thatis lower than the system voltage.

3 The ceramic heater plugs are susceptibleto impact and bending loads. Heater plugs thathave been dropped may be damaged. 1

3 A maximum voltage of 7 V may be appliedto the heater plugs when removed. Highervoltages without cooling air movement canirreparably damage the heater plugs. 1

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Sensors and actuatorsIn the M57D30T2 US engine, themodifications to the sensors and actuators arerestricted to the air intake and exhaust system.Several new components have been added to

this system. The table below provides anoverview. It shows a comparison between theE70 US and E90 US and the EURO4 versionof the ECE variant.

Sensors EURO4 E70 US E90 USOutside temperature sensor 7 7 7

Ambient pressure sensor 7 7 7

Hot-film air mass meter (HFM) 7 7 7

Intake air temperature sensor (in HFM) 7 7 7

Charge air temperature sensor 7 7 7

Boost pressure sensor 7 7 7

Exhaust pressure sensor at exhaust manifold 7 7

Oxygen sensor 7 7 7

Exhaust gas temperature sensor beforeoxidation catalytic converter

7 7 7

Exhaust gas temperature sensor beforediesel particulate filter

7 7 7

Exhaust backpressure sensor before dieselparticulate filter

7 - -

Exhaust differential pressure sensor - 7 7

Temperature sensor afterlow pressure EGR cooler

- 7 -

Temperature sensor afterhigh pressure EGR cooler

- 7 7

Exhaust gas temperature sensor beforeSCR catalytic converter

- 7 7

NOx sensor before SCR catalytic converter - 7 7

NOx sensor after SCR catalytic converter - 7 7

Positional feedback, swirl flaps - 7 7

Positional feedbackhigh pressure EGR valve

- 7 7

Positional feedbacklow pressure EGR valve

- 7 -

Blow-by connection - 7 7

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OBD functionThe engine management has the additionaltask of monitoring all exhaust-relevantsystems to ensure they are functioningcorrectly. This task is known as OnBoardDiagnosis (OBD). The malfunction indicatorlamp (MIL) is activated if the onboarddiagnosis registers a fault.

The events specific to US diesel engines thatcause the MIL to light up are described in thefollowing.

Oxidation catalytic converter

The oxidation catalytic converter is monitoredwith regard to its conversion ability whichdiminishes with ageing. The conversion ofhydrocarbons (HC) during cold start is used asthe indicator as heat is produced as part of the

chemical reaction and it follows a definedtemperature progression after the oxidationcatalytic converter.

The exhaust gas temperature sensor after theoxidation catalytic converter measures thetemperature. The DDE maps the temperatureprogression during cold start and compares itto calculated models. The result determineshow effective the oxidation catalytic converteris operating. A reversible fault is stored if thetemperature progression drops below apredetermined value. If this fault is stilldetermined after two successive dieselparticulate filter regeneration cycles, anirreversible fault is stored and the MIL isactivated.

Actuators EURO4 E70 US E90 USCompressor bypass valve EUV EUV EUVTurbine control valve EPDW EPDW EPDWWastegate EPDW EPDW EPDWThrottle valve EL EL ELSwirl flaps EUV EL ELHigh pressure EGR valve EPDW EL ELLow pressure EGR valve - EPDW EPDWBypass valve for high pressure EGR cooler - EUV EUVSCR metering valve EL EL ELEL = Electrically operated

EUV = Pneumatically operated via electric changeover valve

EPDW = Pneumatically operated via electropneumatic pressure converter

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SCR catalytic converter

The effectiveness of the SCR catalyticconverter is monitored by the two NOxcatalytic converters.

The nitrogen mass is measured before andafter the SCR catalytic converter and a sum isformed over a defined period of time. Theactual reduction is compared with a calculatedvalue that is stored in the DDE.

The following conditions must be met for thispurpose:

• NOx sensors plausible

• Metering active

• Ambient temperature in defined range

• Ambient pressure in defined range

• Regeneration of diesel particulate filter notactive

• SCR catalytic converter temperature indefined range (is calculated by means ofexhaust temperature sensor before SCRcatalytic converter)

• Flow of exhaust gas in defined range.

Monitoring involves four measuring cycles. Areversible fault is stored if the actual value islower than the calculated value. If the fault isdetermined in two successive driving cycles,an irreversible fault is stored and the MIL isactivated.

Long-term adaptation is implemented, wherethe metered quantity of urea-water solution isadapted, to ensure the effectiveness of theSCR catalytic converter over a long period oftime. To execute this adaptation procedure,the signal of the NOx sensor after the SCRcatalytic converter is compared with a

calculated value. If variations occur, themetered quantity is correspondingly adaptedin the short term. The adaptations areevaluated and a correction factor is applied tothe metered quantity.

The operating range for the long-termadaptation is the same as that foreffectiveness monitoring.

A reversible fault is stored if the correctionfactor exceeds a defined threshold. If the faultis determined in two successive driving cycles,an irreversible fault is stored and the MIL isactivated.

Supplying urea-water solution

A supply of a urea-water solution is required toensure efficient operation of the SCR catalyticconverter.

Once the SCR catalytic converter has reacheda certain temperature (calculated by theexhaust gas temperature sensor before theSCR catalytic converter), the metering controlsystem attempts to build up pressure in themetering line. For this purpose, the meteringmodule must be closed and the delivery pumpactuated at a certain speed for a definedperiod of time.

If the defined pressure threshold cannot bereached within a certain time, the meteringmodule is opened in order to vent themetering line. This is followed by a newattempt to build up pressure.

A reversible fault is stored if a defined numberof pressure build-up attempts remainunsuccessful. If the fault is determined in twosuccessive driving cycles, an irreversible faultis stored and the MIL is activated.

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This monitoring takes place only once perdriving cycle before metering begins.Continuous pressure monitoring begins afterthis monitoring run was successful.

A constant pressure of the urea-water solution(5 bar) is required for the selective catalyticreduction process. The actual pressure ismeasured by the pressure sensor in thedelivery module and compared with aminimum and a maximum pressure threshold.A reversible fault is stored if the limits areexceeded for a certain time. If the fault isdetermined in two successive driving cycles,an irreversible fault is stored and the MIL isactivated.

This monitoring run takes place whilemetering is active.

Level measurement in active reservoir

A level sensor with three contacts at differentheights is used for the active reservoir. Theplausibility of the sensor is checked in theevaluator in that it checks whether the signalsare logical. For example, it is improbable thatthe "Full" contact is covered by the solutionwhile the "Empty" contact is not.

In this case, the evaluator sends a plausibilityerror to the DDE. This takes place at a pulseduty factor of 30 % of the PWM signal. Areversible fault is set. If the fault is determinedin two successive driving cycles, an

irreversible fault is stored and the MIL isactivated.

This monitoring procedure only takes place ifthe temperature in the active reservoir isabove a defined value.

If the line between the evaluator and at leastone contact of the level sensor is interrupted,the fault is signalled to the DDE by a PWMsignal with 40 % pulse duty factor. A reversiblefault is set. If the fault is determined in twosuccessive driving cycles, an irreversible faultis stored and the MIL is activated.

Suitable urea-water solution

The SCR system is monitored with regard torefilling with an incorrect medium. Thismonitoring function starts when refilling isdetected. Refilling detection is described inthe section on the SCR system.

Effectiveness monitoring of the SCR catalyticconverter is used for the purpose ofdetermining whether an incorrect medium hasbeen used. An incorrect medium is detected ifthe effectiveness drops below a certain valuewithin a defined period of time after refilling. Areversible fault is set in this case. If the fault isdetermined in two successive driving cycles,an irreversible fault is stored and the MIL isactivated.

In addition, the warning scenario with aremaining range of 200 mls is started.

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NOx sensors

A dew point must be reached for effectiveoperation and therefore also the monitoring ofthe NOx sensor. This ensures that there is nolonger any water in the exhaust system thatcould damage the NOx sensors.

A reversible fault is set if the followingmonitoring functions detect a fault at the NOxsensor. If the fault is determined in twosuccessive driving cycles, an irreversible faultis stored and the MIL is activated.

• Detection signal or correction factorincorrect

• Line break or short-circuit betweenmeasuring probe and control unit of NOxsensor

• Measured value outside the defined rangefor a certain period of time

• Operating temperature is not reached aftera defined heating time

• The distance from the measured value tozero is too great in overrun mode (nonitrogen oxides expected)

• During the transition from load to overrunmode, the signal of the NOx sensor doesnot drop fast enough from 80 % to 50 %(only NOx sensor before SCR catalyticconverter)

• If, despite a peak in the signal of the NOxsensor before the SCR catalytic converter,at least a defined change in the signal of the

NOx sensor after the SCR catalyticconverter is not determined this isinterpreted as implausible.

Exhaust gas recirculation (EGR)

During normal operation, the exhaust gasrecirculation is controlled based on the EGRratio. During regeneration of the dieselparticulate filter, it is conventionally controlledbased on the air mass.

The monitoring function also differs in thisway: During normal operation a fault isdetected when the EGR ratio is above orbelow defined limits for a certain period oftime. This applies to the air mass duringregeneration of the diesel particulate filter.

In order to monitor the high pressure EGRcooler, the temperature after the highpressure EGR cooler is measured with thebypass valve open and close with the enginerunning at idle speed. A fault is detected if thetemperature difference is below a certainvalue.

For the low pressure EGR cooler (only E70),the measured temperature after the lowpressure EGR cooler is compared with acalculate temperature for this position. A faultis detected if the difference exceeds a certainvalue.

Each of these faults is stored reversible. If thefault is determined in two successive drivingcycles, an irreversible fault is stored and theMIL is activated.

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Diesel particulate filter (DPF)

The diesel particulate filter is monitored bymeans of the differential pressure sensor. Ifthe filter is defective, the differential pressurebefore and after the filter will be lower than fora new filter.

Monitoring starts when the flow of exhaust gasand the diesel particulate filter temperatureexceed certain values. A fault is detectedwhen the differential pressure drops below adefined threshold for a certain period of time.

Conversely, an overloaded/clogged dieselparticulate filter is detected when thedifferential pressure exceeds a defined valuefor a certain period of time.

When regeneration of the diesel particulatefilter is started, the time required until theexhaust temperature before the DPF reaches

250 °C is measured. This time is set to zero ifthe engine runs for a longer period of time atidle speed or in overrun mode. A fault isdetected if a defined time is exceeded beforethe temperature of 250 °C is reached. In thisway, the response characteristics of theincrease in exhaust temperature for DPFregeneration are monitored.

The system also monitors whether theexhaust gas temperature before the dieselparticulate filter corresponds to the expectedvalue after a defined period of time. If this is notthe case although the control system hasreached its limits, a fault is detected.

Also in this case, each of these faults is storedreversible. If the fault is determined in twosuccessive driving cycles, an irreversible faultis stored and the MIL is activated.

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Automatic transmission

In view of the high torque developed by theM57D30T2 engine, the GA6HP26TU

gearbox is used, which is normally fitted in 8-cylinder petrol engine vehicles.

Twin damper torque converterThe gearbox is identical to that used in theX5 4.8i; only the torque converter is different.A so-called turbine torsional damper (TTD) isused while a twin damper torque converter isused for diesel engines.

In principle, the twin damper torque converteris a turbine torsional damper with a furtherdamper connected upstream.

The primary side of the first damper isconnected to the converter lockup clutchwhile the secondary side is connected to theprimary side of the second damper. As in theturbine torsional damper, the secondary sideis fixed to the turbine wheel of the torqueconverter.

75 - GA6HP26TU gearbox

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When the converter lockup clutch is open, thepower flow is equal to that of the turbinetorsional damper. The power is transferredfrom the turbine wheel via the second damper(but without damping) to the transmissioninput shaft.

When the converter lockup clutch is closed,the power is transmitted via the first damper

that consists of an annular spring. From herethe power is transmitted to the seconddamper which operationally corresponds tothe turbine torsional damper and also consistsof two annular springs.

These further improved damping propertieseffectively adapt the transmission to theoperational irregularities of the diesel engine.

76 - Twin damper torque converter

Index Explanation Index Explanation1 Annular spring 5 Stator2 Converter housing 6 Transmission input shaft3 Turbine wheel 7 Annular spring assembly4 Impeller

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