w2mercedes w220 20 key intermittent in ignition version 02

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May 2012 Page 1 of 32

W220 2004 S500 Remote Control Key Will Not Work/Rotate/Turn

In Ignition Lock Intermittently BenzWorld Member ricebubbles

Table of Contents 1. Revisions ............................................................................................................................ 1 2. Acknowledgement .............................................................................................................. 1

3. Introduction ........................................................................................................................ 2 4. Benzworld Member Experience With The Problem ............................................................ 2

5. My Experience With The Problem ...................................................................................... 2 6. Parts of a W220 Remote Control Key ................................................................................. 3

7. How the Remote Control Key Works in a W220 ................................................................. 4 8. Key Fob Battery ................................................................................................................. 6

9. Initial Tests To Diagnose An Intermittent Key .................................................................... 6 10. Further Tests To Diagnose An Intermittent Key .............................................................. 6

11. Testing EIS Induction Power Generator Output ............................................................ 10 12. Test of EIS Fuses .......................................................................................................... 18

13. Test of Induced Voltages In Actual OEM Remote Control Key .................................... 18 14. Test of Induced Voltages In Modified Remote Control Key .......................................... 23

15. Initial Conclusion ......................................................................................................... 25 16. Removing the EIS ......................................................................................................... 25

17. Inside the EIS ............................................................................................................... 27 18. Testing EIS in Car ........................................................................................................ 29 19. EIS Test Results............................................................................................................ 29

20. EIS Permanent Failure .................................................................................................. 30 21. Testing EIS on the Bench .............................................................................................. 30

22. Final Conclusion ........................................................................................................... 31

1. Revisions 2012-05-24 Version 01: Original Document

2012-10-13 Version 02: Fixed typo in Table 4. Fuse f87 should have been Fuse f78.

2012-11-13 Version 02a: Added details for removing and investigating EIS.

2012-12-21 Version 02b: Added Final Conclusion.

2. Acknowledgement The main reference was the BenzWorld Forum:

http://www.benzworld.org/forums/w220-s-class/1473416-help-please.html

with special thanks to BenzWorld Member fatrash

http://www.benzworld.org/forums/w220-s-class/1393624-intermittent-key-turning-problem-04-

s500.html bigbodyw140 had intermittent EIS problem with 2004 S500 4Matic.

http://forums.mbworld.org/forums/s-class-w220/222345-s320-cdi-2003-key-does-not-turn-

ignition.html Shaneabbas and zam2000

http://www.benzworld.org/forums/w220-s-class/1300215-cold-weather-electronic-key-

problems.html carbucci

http://www.benzworld.org/forums/w220-s-class/1300215-cold-weather-electronic-key-problems-

3.html Gabby07621 and Triluxor

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DGN for access to E320 and CLK200.

3. Introduction Normally after inserting the correct Remote Control Key in the ignition lock (Electronic

Ignition/Starter Switch (EIS) control module (N73)) it will turn instantly to position 1

(accessories), 2 (ignition on) and position 3 (engine start). However it seems that a common

fault in the W220 occurs whereby the correct key will unlock the doors but once inserted in the

ignition will not rotate and appears frozen. In my case this happened intermittently causing huge

frustration when out travelling. Fortunately on one trip it eventually worked after continually

trying and waiting twenty minutes.

4. Benzworld Member Experience With The Problem zam2000 had intermittent EIS problem. After scanning the forum, and confirm w/ MB Indy shop, look like the EIS is on the way out. For EIS, it's worth it to shop around, and only do it at

Mercedes specialized shop, since you'll need the Star Diagnostic to transfer code from the old

EIS to the new one. Some places charge the green key cost, some don't. Some require new set of

key, other don't. I got quote anywhere from $760 to $3000! MB Tech in Monterey Park (CA)

just ordered part for me. $512 for part, and $260 for labor, can reuse my old keys, and they won't

even charge anything for the green key. (Transport unlock device). I am told that if the

mechanic follow proper procedures, then you can reuse the old keys. However, if they mess up,

or simply want to take short cut, then it'll cost you a new set of key too.

carbucci had intermittent EIS problem with 2003 S430 4Matic. Replaced EIS at MB Dealer and everything OK.

Gabby07621 narrowed the problem to the EIS by warming it with a hairdryer every cold morning.

Triluxor established temperature DOES affect the EIS. Whenever it goes below 70F (21C) the car won't start. As soon as it goes over 74F (23C), it will after a few tries. Above 80F (27C) it

will start EVERY time. In any case, I left the vehicle 3 days at my $tealer (Bill Ussery MB of

Coral Gables) who charged me $300.00 just to say they couldn't find anything wrong with the

ignition. Put the key in, it's immediately recognized. They ran computer tests, no faults

whatsoever. So, they said, drive it for a few days and tell us if the problem resurfaces. Went to

pick it up yesterday at 6:00 pm, made a couple of stops along the way, no problems. This

morning at 7:30, temperature at 73F (23C), the key wasn't recognized at all. So I call the $tealer

once again who said "Bring the car back, we'll trace all the wires and see what's going on.

Incidentally, it may take 5 or 6 hours at $90 an hour." Incredible how Mercedes Benz designed a

system that would prevent anyone from moving the vehicle--including the owner. Well, wound

up taking my car to the $tealer, Bill Ussery in Coral Gables, and they said they'd start by

replacing the EIS... at $1,350. Triluxor hasnt been on BenzWorld since.

5. My Experience With The Problem My first experience with this issue was when my Remote Control Key would not turn in the

ignition in my W220 2003 Update S500L. I had just opened the doors remotely and placed the

key in the ignition and noticed that the steering wheel did not lower automatically as usual. The

dashboard was all lit up as usual. The key would not rotate from position 0 (Locked). Cursing

that the batteries in the key must be faulty, I went inside and recovered the second spare Remote Control Key which is rarely used. By the time I inserted this key in the lock everything

worked OK and I went on my way, later purchasing new batteries for the other key fob.

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The car worked fine with the original key, now with new batteries, for the next two weeks until

once again, first thing in the morning, the key would not turn in the lock. The red light on the

key fob would flash when any of the buttons were pressed. I spent a whole day resoldering the

connections on the key electronic circuit board believing that I had an intermittent connection.

This was rather difficult at my age with failing eyesight and shaky hands. I was rather peeved

when of course it did not fix the problem.

Then after considerable trawling through many BenzWorld threads I tested my car battery with a

digital voltmeter and noticed that voltage after sitting for 24 hours was 12.3V. When I pressed

the remote to open the doors the voltage dropped to below 12V before slowly recovering. I

decided to replace the car battery and was surprised to find that it was still the original German

one from mid 2003 (and had provided service for over 9 years!!). The new battery now reads

12.57V with the car locked and asleep after 24 hours of none use.

Replacing the car battery fixed the problem until a very cold morning a few days later. Once

again the key would not turn in the ignition, which was a potential disaster as we were travelling

interstate and a long way from home and workshop/tools etc. After a lot of cursing and then

waiting for about twenty minutes it decided to work again and we were on our way without

having to summons assistance. The key worked fine for the rest of the day.

The next morning, which was also very cold at 5C, the Remote Control Key refused to work

again. By pure luck I managed to get it to rotate by jiggling it in the ignition lock. It seemed to

me that there must be an electrical switch inside the ignition lock which is activated by inserting

the key, thus powering up the Electronic Ignition/Starting Switch (EIS) and initiating the data

reading circuit, which if it recognises the correct code, allows the key to rotate. I suspected that

this switch had dirty contacts. My guess was that with a low car battery voltage, especially on a

cold morning, there was enough resistance in the switch to prevent the EIS from working

properly. The resistance is probably due to dirt and crud build up after nine years of use. The

external appearance of the ignition lock was quite dirty. I decided to flush the lock with

electrical cleaning spray. I poked a match into the ignition to depress the centre part and flushed

it thoroughly with CRC Mass Air Flow Sensor Cleaner repeating the process several times.

Most of the time the key now operates as intended even with a car battery voltage of 12.2V with

headlights, tail lights and boot/trunk lights operating. However it still occasionally refuses to turn

until you have tried for several minutes. This involves inserting, trying and withdrawing the key

until it eventually operates.

There is obviously something in the electronics which is very marginal and which doesnt need much to trip it from non functioning to functioning. It appears to be very temperature sensitive,

malfunctioning when cold (below about 15C).

6. Parts of a W220 Remote Control Key The four main components of the Remote Control Key (A8/1) are the key fob case, electronic

printed circuit board, the battery holder with fob lid and with two 3V CR2025 button type

batteries, and the mechanical key.

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Figure 1 Button Side of a W220 Remote Control Key (A8/1)

Figure 2 Reverse Side of a W220 Remote Control Key (A8/1)

7. How the Remote Control Key Works in a W220 Reference STAR Diagnosis System (SDS), Xentry, Workshop Information System (WIS).

The Remote Control Key (A8/1) emits radio frequency (RF) (In Australia 315 MHz) frequency

modulated (FM) signals to operate the remote control functions of unlocking, locking, and

boot/trunk opening. The two internal batteries in the key fob are used to power these functions.

If these batteries are weak or flat, the key will not unlock the doors or boot/trunk. A mechanical

key is stored inside the key fob and is provided in the event of this situation occurring.

The Remote Control Key also emits infra red (IR) signals to operate the convenience opening

and closing feature. The IR signals are received by either IR sensor built into the two front door

handles. The key needs to be pointing at the handle and within a few metres for the function to

work. Better range is achieved if the receiving door handle is not in direct sunlight. The two

internal batteries in the key fob are used to power the IR emitter for this function

When a Remote Control Key (or a finger for that matter) is inserted in the electronic ignition

switch (EIS or EZS) control unit (ignition lock) (N73), it operates a switch which activates an

AC generator inside the ignition lock. This generator produces a high frequency (118KHz) sine

wave which is inductively coupled to a small coil in the tip of the key fob.

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Figure 3 Induction Coil on a Remote Control Key PCB

The AC voltage produced in the coil is rectified and the resulting DC voltage is used to power

the Remote Control Key ignition functions. (The induced DC voltage was measured as 7.6V.)

Using a separate inductive power supply very cleverly avoids reliance on the Remote Control

Key batteries and ensures the Remote Control Key will operate the ignition even if it has internal

flat or weak batteries.

Figure 4 Induction Coils on the Barrel of the EIS (N73)

Once powered by the Induction Power Generator the Remote Control Key emits IR signals to,

and receives IR signals from, the Drive Authorisation System (DAS) in the Electronic

Ignition/Starter Switch (EIS) control module (N73). Start-up is enabled only after the transmitter

key (A8/1) is identified by the encrypted data exchange between the

EIS control unit (N73) and the

ME-SFI control unit (N3/10) (with gasoline engine).

If the identification of the transmitter key (A8/1) is valid, the rotary lock of the EIS control unit

(N73) is enabled. The transmitter key (A8/1) can now be turned. Once the correct code is

recognised, the EIS allows the initial start procedures to commence, viz;

rotary lock in EIS released, which allows the key to be turned in the lock to positions 1, 2 and 3, thus starting the car.

steering wheel resumes its operating position (if this function has been previously activated),

engine electric suction fan initiates,

engine control module initiates,

Automatic Climate Control (ACC) initiates,

COMAND system initiates,

gear selector lever lockout mechanism releases,

any stored values for parameters such as seat and mirror positions, ACC settings, and COMAND settings etc. which are associated with this particular key are initiated (if this

function has been previously activated).

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When a non-recognised key, including my Dummy Test Key, is used the EIS Inductive Power

Supply only operates for about 3 to 4 seconds after the key has been inserted into the Ignition

Lock. When the key is not recognised, the Inductive Power Supply reverts to zero output for

about 30 seconds when it generates another short burst of AC power in an attempt to read the

key. I did not establish how many times it continues to do this before cancelling.

When a key is used that is recognised by the EIS, the Inductive Power Supply operates

continuously until the key is removed.

Note the mechanical lock system in the EIS also prevents the Remote Control Key from being

turned back to position 0 (Locked) and withdrawn from the EIS Ignition Lock unless the gear

selector lever is in P or Park.

8. Key Fob Battery After wasting a lot of time I discovered the battery in the Remote Control Key fob has nothing to

do with the key's ability to start the engine. There is an inductive coil inside the ignition switch

(EIS) that powers the key for starting. The Remote Control Key battery is only used for the

remote control functions.

Changing the batteries in the Remote Control Key fob is very simple. A W220 key takes two 3V

CR2025 button type batteries which are readily available.

9. Initial Tests To Diagnose An Intermittent Key If you are experiencing the issue where the key will not routinely turn once inserted into the

ignition lock then the following tests should be performed at the beginning of your

investigations.

Can you lock/unlock the car with the key fob or do you have to lock and unlock the car with the metal key?

When you insert the key in the ignition are you able to move it to position 1, 2 and 3?

Do you have a second key and have you tried starting with the second key?

Does the centre part of the ignition lock appear dirty?

10. Further Tests To Diagnose An Intermittent Key If the Remote Control Key appears to be frozen and will not turn to position 1, (accessories),

position 2 (ignition on) or position 3 (starting position) it means that the key is not recognized by

the car. This also happens if you try to use a Remote Control Key from another car.

Check these items in the following order.

10.1. Check Car Battery Voltage

According to BenzWorld posters, by far the most common issue causing this problem is that

your car battery is not putting out enough voltage.

It appears that the ignition circuit is quite sensitive to car battery voltage. The car will unlock and the instrument cluster will light up when you enter the car. You may have

even been able to start the car just minutes before and the battery may appear to be good

and strong otherwise, and yet it may be weak under load and is not putting out the

minimum required voltage for the ignition switch to read the key.

Note that the drain/load on the car battery just after unlocking the doors with the remote is significant and can cause the voltage from a weak battery to drop below the required

level for the ignition to work. On my car, as the remote unlock signal is received and

recognized, the car activates the central unlocking system and unlocks the doors, operates

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the headlights and tail lights for 20 seconds, operates the interior lights if it is dark

enough for 20 seconds, flashes the turn indicator lights, and starts the Electronic Ignition

System (EIS) and initiates several other control units as described above. Consequently

the car battery is really hammered for a few minutes after unlocking until the load drops

off as the electronics in the car settle down. The battery voltage may recover enough for

the ignition to now work. This gives the impression of a random fault.

Other signs of a weak car battery which you may have experienced include, slower rising of the door locks, slower remote response to open boot/trunk and random and sudden

appearance of BAS/EPS malfunction indication while driving or with the car started.

This BAS/EPS malfunction indication will disappear once the ignition is turned off and

the car is later restarted.

Once sufficient voltage is made available the key will automatically sync with the car and you will be able to turn the key instantly after inserting the key fob.

A simple test on the car battery is to measure the voltage first thing in the morning after the

vehicle has been sitting asleep for 12 hours or so. The night before set up your voltmeter on long

leads so that the boot/trunk lid can be closed and the car locked. Place the voltmeter outside the

vehicle and do not activate any functions prior to taking your reading. The voltage should be at

least 12.4V. Make sure to rectify a weak battery condition quickly as you do not want to be

replacing an over worked alternator as well.

10.1.1. Results of Car Battery Voltage Test

The new battery in my W220 reads 12.57V with the car locked and asleep after 24 hours of none use.

10.2. Check Car Charging Function

One additional thing to check is the charging circuit. Some "smart" battery chargers will do this

for you. After a good drive of 60 minutes or so the car battery should be fully charged and read

at least 14.2V with the car running and the charger operating. Turn off large power consumers

such as headlights for this test. If the battery does not have a healthy voltage, suspect the

alternator and associated charging circuits.

10.3. Check Car Battery

You can also test the battery itself with a hydrometer or by performing a load test. Either will

show a battery that has outlived its usefulness. There is a pretty good tutorial on batteries at:

http://www.batterystuff.com/tutorial_battery.html and another one for the hydrometer test at:

http://autorepair.about.com/library/.../aa101604c.htm. There's a "poor man's load test" video at:

http://www.youtube.com/watch?v=viltQBg2jOQ

10.4. Disconnecting the Car Battery

Of course replacing the car battery means that you may have to go through the entire

reset/synchronisation procedure (windows, seats, mirrors, sunroof, steering angle sensor and

BAS/ESP malfunction indicator). See post #14 at

http://www.benzworld.org/forums/w220...st2216730.html. For more on resetting see;

http://www.benzworld.org/forums/w208...procedure.html.

If you want to avoid the resynchronization, temporarily connect another 12V battery across the

car battery leads before disconnecting them to act as a backup battery. The backup battery can be

a low power battery as long as you do not open, lock or unlock any doors or activate any circuits

whilst it is connected. I use a 12V 5A-Hr House Alarm Battery connected to my charging point

which I installed in the engine compartment. DO NOT USE a battery charger as a backup or at

any time with the car battery disconnected, as the voltage WILL be too high and WILL damage

something. The technique is to ensure that the car is asleep with the boot/trunk lid open and the

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bonnet/hood open. I also have the drivers window open. I connect my 12V 5A-Hr House Alarm Battery to the charging point in the engine compartment and then disconnect the car

battery in the boot/trunk. Make sure nothing gets activated while the backup battery is

connected, especially lock/unlock, headlights or ignition and starter motor.

10.4.1. Charging Point Inside Engine Compartment

This was a good idea I picked up from BenzWorld posters in threads where owners have had a

flat battery, but could not get into the trunk/boot to charge up. All you need to do is open the

hood/bonnet, remove the lid from the Right (Passenger side for LHD, Drivers side for RHD)

Fuse Box. Connect the negative lead from the charger to the earth point just in front of the fuse

box (or any good earth). Connect the positive lead from the charger to fuse f33, 40A, that runs

air conditioner and blower motor and is constant live. I have soldered a small quick connect tag

onto fuse f33 so that I can simply plug my battery charger onto this tag. If charging at this point

only use a low charge rate setting, eg

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10.5.1. Specified W220 Quiescent Current Draw/Load

Reference: Star Diagnosis System (SDS) Xentry Workshop Information System (WIS) the

quiescent current at the battery terminal for a W220 after the car has been locked for at least 20

minutes and the car has gone to sleep, should be no more than 0.050A or 50mA.

If testing at individual fuses each fuse quiescent current should be no more than 0.020-0.030A or

20-30mA.

10.5.2. Measure Quiescent Current Draw/Load

There are several good links to testing car battery quiescent current draw (also called parasitic

drain).

http://www.benzworld.org/forums/w220-s-class/1491289-how-measure-quiescent-current-

battery-die.html

How to Find a Parasitic Battery Drain - wikiHow

My version.

http://www.benzworld.org/forums/w220-s-class/1666913-w220-s500-measuring-quiescent-

current-parasitic.html

10.5.3. Results of Car Battery Quiescent Current Draw/Load Tests

The quiescent current draw/load in my S500L is 26-32mA, which is well within the

specification. [

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Do not buy a used key from eBay etc. Keys CANNOT be reprogrammed. If you just want to

give your key fob a facelift, new outer key cases, with or without a metal key blank, are readily

available on eBay for about $20. You then just swap over your keys electronics.

A new key fob with electronics is $450.00 from MB and is already programmed at the factory.

BenzWorld Member fatrash has repaired faulty solder joints in his key electronics, see; http://www.benzworld.org/forums/w220-s-class/1269278-electronic-key-not-working.html

Figure 8 Resoldering Key Electronics (NB Different Key PCB to 2003 Update S500L)

Note the difference between fatrashs W220 (unknown year) and my 2003 Remote Control Key.

Figure 9 (Left) fatrashs (unknown model and year) and (Right) my W220 2003 S500 Remote Control Key

The two large areas on the pcbs are to make contact with the battery pack.

10.8. Faulty Ignition Switch

If the battery is putting out sufficient voltage and both keys do not work then the ignition switch

is most likely at fault. If it is not a dirty switch or the switch doesnt respond to being flushed/cleaned then it is most likely you need a new ignition which is going to be an expensive

proposition.

11. Testing EIS Induction Power Generator Output In order to investigate the performance of the Induction Power Generator I decided to measure

the AC signal produced by the ignition lock (Electronic Ignition/Starter Switch (EIS) control

module (N73)).

11.1. Construction of Dummy Test Key

Using parts from an old dismantled electrical transformer, I constructed a small coil on the end

of an old paint brush. I ground the end of the paint brush down to a cylinder of about 3mm

diameter. I added a single piece of scrap transformer metal to the wooden cylinder to act as a

core and bound both together with masking tape. This became the former for the coil and

provided a nice winding surface. I wound approximately a thousand turns of 1.1mm diameter

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enamel insulated wire onto the former and soldered some insulated flexible wires for the test

connections.

Figure 10 Test Induction Coil

The exposed coil and connections were wrapped in masking tape and were inserted into an old

empty key fob thus making a dummy test key.

Figure 11 Test Induction Coil Inserted Into an Empty Key Fob

11.2. Baseline Test Using Dummy Test Key

In order to establish a baseline I decided to initially test the Induction Power Generator in our

2008 W204 C220 CDI vehicle. This immediately proved interesting as my Dummy Test Key

once inserted into the lock was able to rotate to positions 1 and 2 without the Drive Authorisation

System being activated. In the W204 there is not the mechanical restriction on key rotation as in

the W220. I do not know why this is the case as the car could still not be taken out of Park.

The AC voltage produced in the coil in my Dummy Test Key by the EIS Induction Power

Generator was measured with a Digital Volt Meter (DVM) and a Cathode Ray Oscilloscope

(CRO) in both my W204 and W220 vehicles. The DVM readings proved to be unreliable, most

likely due to the high frequency of the signals exceeding the DVMs capability. The DVM readings were not analysed.

Note the actual voltages as measured with the Dummy Test Key are completely arbitrary and are

dependent on the number of turns wound on the Dummy Test Key coil. They are useful for

comparison purposes only.

11.3. Test 01 Using Dummy Test Key

Test 01 conditions were:

Tests conducted 09:30 A.M. 28th May 2012.

Vehicles tested: W204 2008 C220 CDI and W220 2003 Update S500L.

Both vehicles had been standing overnight.

Weather cold with ambient 8C.

Both vehicles were tested 5 minutes after unlocking with drivers door open.

W204 C220 Battery Voltage: 12.31V. (Original 2008 battery.)

W220 S500L Battery Voltage: 12.33V. (New battery May 2012.)

W204 C220 Key worked OK.

W220 S500L Key would not initially turn in Lock. After several minutes the key started working again.

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11.3.1. Baseline Tests on W204 C220

Figure 12 Test 01 DVM Reading Dummy Test Key AC Output in W204 C220

Figure 13 Test 01 CRO Reading Dummy Test Key AC Output in W204 C220

CRO Scale: 1V/division with 10x Probe = 10V/division and 5s/division

11.3.2. Now Repeat Tests On W220 S500L

Figure 14 Test 01 DVM Reading Dummy Test Key AC Output in W220 S500L

Figure 15 Test 01 CRO Reading Dummy Test Key AC Output in W220 S500L


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11.3.3. Comparison of W204 and W220 with CRO on Same Scale.

Figure 16 Test 01 Comparison of W204 C220 (Left) and W220 S500L (Right) with CRO on same scale


11.3.4. Summary of Test 01 Results Using Dummy Test Key

Note the actual voltages as measured are completely arbitrary and are dependent on the number

of turns wound on the Dummy Test Key coil. They are useful for comparison purposes only.

Test 01

W204

2008 C220 CDI

Ambient 8C

Test 01

W220

2003 Update S500L

(When Ignition was

not working.)

Ambient 8C

Test 01

W220

2003 Update S500L

(When Ignition was

working.)

Ambient 8C

DVM

AC Volts 8.0V 5.6V 5.6V

CRO

AC Amplitude

Peak to Peak

85V p-p 63V p-p 63V p-p

Calculated CRO

AC Amplitude 30Vrms 22Vrms 22Vrms

CRO

AC Timing

Period

8.5s 8.5s 8.5s

Calculated CRO

AC Frequency 118KHz 118KHz 118KHz

Table 1 Summary of Test 01 Results Using Dummy Test Key

11.3.5. Test 01 Conclusion

Note there was no difference in the W220 Key working/not working results because you can

never be sure whether the key is working or not when using the Dummy Test Key as the car

cannot read any key code and therefore doesnt respond.

After inserting the Remote Control Key and finding it didnt work I removed it, inserted the Dummy Test Key and performed the W220 2003 Update S500L (When Ignition was not working.) tests. Within a few minutes I tried the Remote Control Key again and this time it worked and then retested with the Dummy Test Key with the same test results.

The voltage from the W220 EIS Induction Power Generator is only 74% of the W204 EIS

Induction Power Generator. Whether this is significant or not I do not know, however, because

the problem is intermittent, it could be that the voltage from the Induction Power Generator is

borderline and thus when combined with a cold battery and lower battery voltage it causes the

Remote Control Key to not be authorised.

Because I get the same intermittent result with both Remote Control Keys, I suspect they are not

causing the intermittent problem. It is very unlikely that both keys would have the same issue.

There seems to be something which is causing the output voltage of the W220 Electronic

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Ignition System (EIS) Induction Power Generator to be low. The culprit is most likely in the EIS

itself rather than in the communication systems.

I will repeat the tests later in the day when things have warmed up a bit and the key function is

more reliable.

11.4. Test 02 Using Dummy Test Key


Tests conducted 03:00 P.M. 28th May 2012

Vehicles tested: W204 2008 C220 CDI and W220 2003 Update S500L.

Both vehicles had been standing overnight and all day and not driven.

Weather cool with ambient 14.5C.


W204 C220 Battery Voltage: 12.37V.

W220 S500L Battery Voltage: 12.50V.

W204 C220 Key worked OK.

W220 S500L Key worked OK.

11.4.1. Test 02 on W204

During these tests the DVM seemed to fluctuate a lot so I only analysed the CRO readings.

Figure 17 Test 02 CRO Reading Dummy Test Key AC Output in W204


11.4.2. Test 02 on W220

Figure 18 Test 02 CRO Reading Dummy Test Key AC Output in W220





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11.4.4. Summary of Test 02 Results Using Dummy Test Key



Test 02

W204

2008 C220 CDI

Ambient 14.5C

Test 02

W220

2003 Update S500L

(When Ignition was

not working.)

Ambient 14.5C

Test 02

W220

2003 Update S500L

(When Ignition was

working.)

Ambient 14.5C

DVM

AC Volts Not Reliable N/A Not Reliable

CRO

AC Amplitude

Peak to Peak

85Vp-p N/A 63Vp-p

Calculated CRO

AC Amplitude 30Vrms N/A 22Vrms

CRO

AC Timing

Period

8.5s N/A 8.5s

Calculated CRO

AC Frequency 118KHz N/A 118KHz


11.4.5. Test 02 Conclusion

The Dummy Test Key induced coil voltages as measured by the DVM in both the W204 and

W220 were higher than in the morning Test 01, but both readings fluctuated markedly. They

have been discarded. The CRO readings on the other hand were very stable and exactly the same

as for Test 01. Once again the W220 Induction Power Generator is only 73-74% of the W204

Induction Power Generator Voltage.

The next step is to measure several other MBs of similar vintage. Unfortunately I do not know

anyone with another W220.

11.5. Test 03 on Friends E320 and CLK200 Using Dummy Test Key


Tests conducted 11:00 A.M. 22nd June 2012

Vehicles tested: W211 2004 E320 and W209 2005 CLK200 Kompressor

Both vehicles had been standing overnight and had not been driven.

Weather cold and wet with ambient 10C.


11.5.1. Test 03 on W211 E320

Figure 20 Test 03 on W211 E320

Created 24th


Figure 21 Test 03 DVM Reading Dummy Test Key AC Output in W211 E320

Figure 22 Test 03 CRO Reading Dummy Test Key AC Output in W211 E320


11.5.2. Test 03 on W209 CLK200 Kompressor

Figure 23 Test 03 on W209 CLK200K

Figure 24 Test 03 A2 DVM Reading Dummy Test Key AC Output in W209 CLK200K

Figure 25 Test 03 CRO Reading Dummy Test Key AC Output in W209 CLK200K


Created 24th


11.5.3. Comparison of Test Results for W204 C220, W211 E320, W209 CLK200K and W220 S500L,



Summary of Test 01 and 03 Results Using Dummy Test Key for W204 C220, W211 E320,

W209 CLK200K and W220 S500L, with CRO on Same Scale.

Figure 26 Left to Right

W204 C220, W211 E320 and W209 CLK200K, W220 S500L

with CRO on same scale


Test 01

W204

2008

C220 CDI

Ambient 14.5C

Test 03

W211

2004

E320

Ambient 10C

Test 03

W209

2005 CLK200K

Ambient 10C

Test 01

W220

2003 Update

S500L

Ambient 14.5C

DVM

AC Volts 8.0Vrms 10.7Vrms 11.7Vrms 5.6Vrms

CRO

AC Amplitude

Peak to Peak

85Vp-p 85Vp-p 87Vp-p 63Vp-p

Calculated CRO

AC Amplitude 30Vrms 30Vrms 31Vrms 22Vrms

CRO

AC Timing

Period

8.5s 8.5s 8.5s 8.5s

Calculated CRO

AC Frequency 118KHz 118KHz 118KHz 118KHz

Normalised

Comparison 97% 97% 100% 71%


11.5.4. Test Conclusion

The Dummy Test Key induced coil voltages as measured by the CRO were very stable and

consistent. The W220 Induction Power Generator output is only about 71% when compared to

three other equal vintage Mercedes Benz vehicles.

It seems that the EIS Induction Power Generator output is reduced for some reason. This could

be high resistance fuses, fuse connections or cable connectors in the appropriate EIS supply

lines. It may also be a faulty voltage regulator in the supply to the EIS Induction Power

Generator circuit.

Created 24th


12. Test of EIS Fuses

12.1. EIS Wiring Diagram

Figure 27 EIS Wiring Diagram

The voltage drop across f78/7.5A (FB Cockpit Left (RHD)) was measured with the key out, and

key in.

Battery Side of f78 EIS Side of f78

Key Out 12.69V 12.69V

Key In and Not Operational 12.60V 12.58V

Key In and Operational 12.54V 12.52V

Table 4 Voltage Drop Across f78/7.5A

12.2. Conclusion

The voltage drop across f78 seems reasonable. The voltage drop across X4/10 f2/60A and

connectors Z4/3 and W36/2 were not measured.

13. Test of Induced Voltages In Actual OEM Remote Control Key

The tests conducted with the Dummy Test Key were useful to establish that the EIS was

producing an AC frequency in the Induction Power Supply and that it was being inductively

coupled into a Remote Control Key once inserted into the lock. The Dummy Test Key also

provided useful comparison results between similar vintage Mercedes vehicles, albeit not exactly

the same model.

These Dummy Test Key tests were open circuit tests, ie the coil had no load connected to it and any induced voltage thus produced no current.

I decided to measure the voltage induced in an actual Remote Control Key by the EIS once the

key is inserted into the lock. This type of test is a fully loaded test, ie the internal coil is connected to its normal circuits and thus any induced voltage will produce current and activate

Created 24th


the circuits. It is a more meaningful test but more difficult to execute. It requires some very

careful and fiddly soldering and should only be undertaken by someone with considerable

electronic experience. Things to avoid are damage caused by electrostatic voltages, excess heat

and rough or splattered soldering.

As explained previously the EIS generates a 118KHz sine wave which is inductively picked up

in a small coil in the tip of the Remote Control Key fob. The coil is connected to the two tabs at

the left edge of the coil in the next figure. The tab at the right end of the coil is not connected and

is just for fastening that end of the coil.

Figure 28 Remote Control Key Induction Coil Wiring Diagram

I traced the induction coil connections as far as possible. Some tracks disappear under surface

mount components, and the coil is connected to a diode and what I suspect is a zener diode

resulting in a roughly regulated half wave DC power supply. The voltage produced cannot

exceed the maximum voltage rating marked on the large electrolytic capacitor, the large yellow

component shown just below the coil in the next figure.

Figure 29 Battery Side of Remote Control Key PCB Showing Induction Coil

The capacitor has a value of 47F 10V and is used to store the DC voltage produced. Its time constant is many minutes, ie it holds the voltage charge and powers the key electronics long after

the EIS has stopped generating the AC frequency.

I soldered two wires across the coil (white (AC) and black (0V)) and also one wire (red (+V)) on

to the (red band) end of the capacitor. The modified key could still be inserted into the key fob

but without the battery holder and batteries. These are not needed anyway.

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Figure 30 Battery Side of Remote Control Key PCB Showing Test Wires Soldered Across the Induction Coil

and the Storage Capacitor

13.1. Test 04 Using S500L OEM Remote Control Key


Tests conducted 09:00 A.M. 26th June 2012

Vehicles tested: W220 S500L and W204 C220 CDI

Both vehicles had been standing overnight and had not been driven.

Weather cold and wet with ambient 11C.


The S500L OEM Remote Control Key would obviously not operate the W204 EIS.

The S500L OEM Remote Control Key would not turn in the W220 EIS.

13.1.1. Test 04 on W220 S500L

Figure 31 Test 04 on W220 S500L

Figure 32 Test 04 DVM Reading S500L OEM Remote Control Key DC Output in W220 S500L

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Figure 33 Test 04 CRO Reading S500L OEM Remote Control Key AC Output in W220 S500L


13.1.2. Test 04 on W204 C220 CDI

Figure 34 Test 04 on W204 C220 CDI

Figure 35 Test 04 DVM Reading S500L OEM Remote Control Key DC Output in W204 C220 CDI

Figure 36 Test 04 CRO Reading S500L OEM Remote Control Key AC Output in W204 C220 CDI



The voltages as measured are as accurate as my instruments. Note the flattened top of the induced AC voltage is due to the loading of the half wave rectification circuit.



Test 04

W204

2008 C220 CDI

Ambient 11C

Test 04

W220

2003 Update S500L

(When Ignition was

not working.)

Ambient 11C

DVM

DC Volts 7.60V 7.50V

CRO

AC Amplitude

Peak to Peak

26Vp-p 25Vp-p

CRO 8.5s 8.5s

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Test 04

W204

2008 C220 CDI

Ambient 11C

Test 04

W220

2003 Update S500L

(When Ignition was

not working.)

Ambient 11C

AC Timing

Period

Calculated CRO

AC Frequency 118KHz 118KHz

Table 5 Summary of Test 04 Results Using S500L OEM Remote Control Key

13.2. Test 05 Using S500L OEM Remote Control Key

The test using the S500L OEM Remote Control Key was repeated later in the day when the key

was functioning correctly in the S500L EIS.


Tests conducted 18:30 26th June 2012

Vehicles tested: W220 S500L.

The vehicle had been standing overnight and had not been driven.

Weather cold and wet with ambient 12.9C.

The vehicle was tested 5 minutes after unlocking with drivers door open.

All functions of the Remote Control Key were operating correctly.

13.2.1. Test 05 on W220 S500L

Figure 38 Test 05 DVM Reading S500L OEM Remote Control Key DC Output in W220 S500L

Figure 39 Test 05 CRO Reading S500L OEM Remote Control Key AC Output in W220 S500L


Test 04

W204

2008 C220 CDI

Ambient 11C

Test 04

W220

2003 Update S500L

(When Ignition was

not working.)

Ambient 11C

Test 05

W220

2003 Update S500L

(When Ignition was

working.)

Ambient 12.9C

DVM

DC Volts 7.60V 7.50V 7.56V*

CRO 26Vp-p 25Vp-p 24Vp-p

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Test 04

W204

2008 C220 CDI

Ambient 11C

Test 04

W220

2003 Update S500L

(When Ignition was

not working.)

Ambient 11C

Test 05

W220

2003 Update S500L

(When Ignition was

working.)

Ambient 12.9C

AC Amplitude

Peak to Peak

CRO

AC Timing

Period

8.5s 8.5s 8.5s

Calculated CRO

AC Frequency 118KHz 118KHz 118KHz

Table 6 Summary of Test 05 Results Using S500L OEM Remote Control Key

* The initial voltage measured was 7.59V and it immediately drops to 7.50 and then recovers to

7.56V within a minute.


The induced voltage in the Remote Control Key seems below what it should be and certainly

below the voltage induced in other similar vintage vehicles. The electronics in the Remote

Control Key may be sensitive to low voltage and thus not communicating with the EIS

adequately and thus preventing authorisation.

14. Test of Induced Voltages In Modified Remote Control Key

I decided to add an extra 10% more turns to the induction coil in one of my W220 OEM Remote

Control Keys to see if this would improve the performance of the key once inserted into the EIS.

14.1. Rewinding Remote Control Key Induction Coil

The Original Equipment Manufacturer (OEM) coil contains 137 turns of enamel insulated copper

wire of 0.09mm diameter. It has a resistance of 3.1 Ohms. In removing the OEM coil I

damaged the windings and was forced to rewind anyway. It was rather fiddly and required a

jewellers magnifier headset and a very fine soldering tip to do.

I used 0.11mm diameter wire from an old transformer. About 1.2m of wire is needed and goes

on in two layers starting at the tab at the upper right end in the next figure and finishing at the

lower right tab. The wiring is anti-clockwise looking from the double tab end. I suspect the

wiring orientation doesnt matter but follow the start and finish winding points as per the OEM coil just to be sure.

Figure 40 Induction Coil Former in Remote Control Key

Be careful not to damage the very brittle ferrite rod core sitting in the plastic former. I did and

had to super glue it back together.

Created 24th


137 + 10% = 150 turns. Open circuit voltage should increase by 10%.

Figure 41 Remote Control Key Induction Coil Rewound with 150 Turns

14.1.1. Test 06 on W220 S500L


Tests conducted 11:30 27th June 2012

Vehicles tested: W220 S500L.

The vehicle had been standing overnight and had not been driven.

Weather cold with ambient 11.0C.

The vehicle was tested 5 minutes after unlocking with drivers door open.

The Remote Control Key was not working at the beginning of the test but just decided to work after a minute or so.

Figure 42 Test 06 DVM Reading S500L Modified (150T) Remote Control Key DC Output in W220 S500L

Test 05

W220

2003 Update S500L

OEM Coil

(When Ignition was

not working.)

Ambient 11.0C

Test 06

W220

2003 Update S500L

Modified Coil 150T

(When Ignition was

not working.)

Ambient 11.0C

Test 06

W220

2003 Update S500L

Modified Coil 150T

(When Ignition was

working.)

Ambient 11.0C

DVM

DC Volts 7.50V 7.60V 7.60V

CRO

AC Amplitude

Peak to Peak

25Vp-p Not Measured Not Measured

CRO

AC Timing

Period

8.5s Not Measured

Calculated CRO

AC Frequency 118KHz Not Measured

Table 7 Summary of Test 06 Results Using S500L Modified (150T) Remote Control Key


The induced voltage now limits at 7.60V most of the time and is obviously the zener diode

voltage regulator doing its job. There was no apparent difference with the working or not working issue so the key can be ruled out as the cause of the problem.

Created 24th


15. Initial Conclusion Having ruled out car battery condition, remote control keys, and quiescent current drain on the

car battery as the culprits, it remains to investigate the Electronic Ignition System (EIS or EZS)

itself. There is obviously something in the EIS which is sensitive to temperature and is most

likely a poor solder joint or a connector.

However access to the EIS in a RHD W220 is not explained in WIS. For a LHD W220 the

procedure involves removing the centre COMAND system and removing the EIS through that

aperture. For a RHD it seems that access is only available through the Instrument Cluster

aperture.

At the moment I keep putting this project off for another day. To be continued.

Later Note for Version 02b: Eventually I had no choice but to face up to the problem as the EIS

failed completely.

16. Removing the EIS Turns out it was an easy job for a RHD car (probably much easier than a LHD car) to remove the

EIS.

The first step was to remove the Glove Box so that the two nuts securing the Burred Walnut strip

across the dash could be removed. Then the Walnut strip was removed making it easier to

extract the Instrument Cluster.

For a RHD car the Instrument Cluster is removed using special tools or in my case homemade

ones fashioned out of 1mm thick sheet aluminium.

Figure 43 Home Made Tools for Removing Instrument Cluster

When inserted into the slots on each side of the Instrument Cluster they release plastic retaining

clips. The left hand clip took much persuading but eventually released.

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Figure 44 Retaining Clip in Instrument Cluster

I also made a tool from several pieces of PVC pipe for unscrewing the EIS bezel.

Figure 45 Home Made EIS Bezel Unscrewing Tool

The bezel was easily unscrewed.

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Figure 46 Bezel Unscrewing Tool Inserted in EIS

Then it was an easy matter to reach inside and extract the EIS to the point where the connectors

could be removed. The mechanical rod which activates the Transmission Lock was also

disconnected.

Figure 47 Connectors Removed From EIS

Figure 48 Three Views of the EIS

17. Inside the EIS Once the EIS was on the work bench two small Torx screws were removed so that the EIS could

be opened.

Figure 49 Inside the EIS

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Figure 50 Top and Bottom Views of the EIS PCBs

Three solder joints on the solenoid coil were unsoldered to allow the three pcbs to lay flat.

Figure 51 EIS PCBs Laid Flat

It is hard to see in the photos but several of the solder joints had what looked like green verdigree

corrosion on them.

Figure 52 Close-up of EIS Centre PCB and Solder Joints

I spent several hours using a jewellers head piece magnifier and my finest tip soldering iron, resoldering as many joints as I could. Keep in mind that the electronic components are very

sensitive to electrostatic discharge and can be permanently damaged if care is not taken. Prior to

touching the pcbs always grasp an earth point first. Any surplus solder flux was washed off with cleaner.

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18. Testing EIS in Car In order to test the EIS in situ I added several wires to monitor the voltages and the data on the

CAN Buses and then jury rigged the EIS into the car.

Figure 53 EIS Under Test In Situ

19. EIS Test Results The CAN B (Interior) data matched the specification in terms of voltages, but of course you

cannot tell what the signals actually mean.

Figure 54 Typical Specification for CAN B Data Levels

Figure 55 CAN-B Low (Left) and CAN-B High (Right) As Measured (Scale 2V/div)

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It was easy to generate other CAN B signals, eg pressing the boot/trunk open button on the

remote control key produced a burst of data.

There are no CAN C (engine) signals until the key is turned to position 2 (Ignition).

20. EIS Permanent Failure I was extremely careful not to create any short circuits or damage the pcb during the resoldering

of the joints. However when I reinserted the EIS into the car the hex mos fet power transistor

which activates the mechanical rotation lock solenoid became extremely hot. I could smell the

heat and then burnt my finger on it when investigating. Needless to say, it was completely

stuffed when I checked.

21. Testing EIS on the Bench I spent ages researching the main components in the EIS which helped understand what was

meant to happen in the electronics.

I will not report all my results but just in case anyone is interested here are some of the

components.

Motorola SC510108CFUis a 64pin microprocessor. (There are two of these in my EIS.) (I could not find a pin configuration diagram identifying pin functions.)

PCA82C250 is a 8 pin Philips Can Controller Interface. It provides differential transmit and receive to the CAN-C (Engine) bus.

TJA1054 is a 14 pin Philips Fault-tolerant CAN Transceiver. . It provides differential transmit and receive to the CAN-B (Interior) bus.

42760V5 is a 5 pin 5V Regulator in a TO252-5 case.

IR322A is a hexfet power mosfet in a TO252-AA case.

The circuit diagram for the N73 EIS was shown earlier. Here are the pin diagrams for the

connectors.

Figure 56 Rear View Showing Fixed Connectors for EIS

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Figure 57 Rear View of Fixed Connectors for EIS

Figure 58 Circuit Diagram for A Connector for EIS

Also shown for interest is the circuit diagram for the EIS Lock Solenoid. A signal from one of

the microprocessors turns on the hex mosfet which activates the solenoid and allows the key to

rotate in the EIS.

Figure 59 Circuit Diagram for EIS Lock Solenoid

22. Final Conclusion After several weeks of investigation I had had enough and called it quits. I arranged for the car

to be towed to an independent MB Workshop and requested that they fit a new EIS. As others

have pointed out, being a security item, you need to produce registration and ownership papers

and sign a release document before a new EIS will be ordered.

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I provided the VIN numbers and other details and a new EIS eventually arrived along with a

Workshop Key (blue in colour) which is used to code the new EIS and associated Keys.

The new EIS would not work with either of my old remote control keys and so we had to order a

new key. I will order a spare key later.

The new key worked in the EIS and would start the engine but the auto transmission would not

engage. The EIS (N73) and/or the ME-SFI control unit (N3/10) obviously sends a coded signal

to the Transmission Control Module.

Eventually after several weeks of investigation the MB Technician ordered another EIS which

this time came with an orange coloured Workshop Key. This time everything worked as

intended. I paid the bill, $2,900.00, and thankfully we are back driving in super luxury again. It

is amazing how much I missed my car. It was out of action for 11 weeks plus had intermittent

EIS operation for nearly one year.

w2mercedes w220 20 key intermittent in ignition version 02

Documents

w220 remote control

intermittent key

s500 remote control

modified remote control

remote control key works

test of eis fuses

eis test results

actual oem remote control