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Anti-lock Braking System Anti-lock Braking System
[ABS][ABS]
TATA MOTORS LIMITEDCustomer Service
Commercial Vehicle Business UnitMumbai, Jamshedpur, Pune, Lucknow & Dharwad
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S.No
Regulation Implementation Date
Vehicle Category
Affected Vehicles – (Identified by NPI / Mktg)
1 IS 11852-2001 norms
Apr’06(Already Implemented)
All vehicles
All Vehicles
2 ABS on vehicles carrying hazardous goods & LPG containers
Oct’06 N2 & N3 (Other than Tractor – Trailers)
LPT 1613 – BS II, LPT 1615 – BS III, LPT 2515 – BS II, LPT 2518 – BS III, SE 1613, LPT 709 – BS II, LPT 712 - BS III, LPT 909 – BS II, LPT 912 – BSIII, LPT 1109 - BS II, LPT 1112 – BS III, SFC 410 – BS III
3 Automatic adjusters
Apr’07 All vehicles
All Vehicles
4 ABS on double decked transport vehicles
Oct’07 N3 Car Carriers – LPO 1510 - BS II, LPO 1610 – BS II
5 ABS on Tractor-Trailers
Oct’07 N3 LPS 4018 - BS II & BS III,LPS 3516 - BS II & BS III
6 ABS on Tourist Buses
Oct’07 M3 LPO 1616 – BS II, High deck Bus, LP 709 – BS II & LP 712 - BS III, LP 1109 - BS II & LPT 1112 - BS III,LP 1510 & LP 1512 – BS II etc
Regulatory Road Map on Brakes in Domestic vehicles
ABS is currently mandatory on all Heavy vehicles in Europe, USA, China, Japan, Korea and Australia. This trend is rapidly catching over in developing
countries also.
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Why Wheel Lock during Braking?
When the Brake force applied is more than the friction between Road and Tire then than
wheel will lock.
Wheels will lock under critical Braking systems like
Panic Brake due to unanticipated obstacle
Braking on wet or Slippery surfaces
Effects of Wheel Lock:
Front wheel locking – Loss of Steerability & Vehicle going out of control
Rear wheel locking – Loss of stability, Jackknifing in Tractors
More Tyre wear - Strong Abrasion of Tyres
How to avoid Wheel lock
Individual wheel brake pressure to be controlled precisely based on - Road condition
Load condition
Speed of the vehicle
Brake lining condition
ABS Basics
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ABS – Basics
Driver presses brake pedal
Brake chamber pressure increases
Brake torque
Brake chamber size,Slack adjuster length,Foundation brake geometryand lining material friction
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When a Wheel can Lock During Braking
Fx max = Co-efficient of friction between Road and Tyre () X Fz;
Fx required to keep the wheel rotating =Brake Torque / Tyre Dynamic Radius
When Fx required > Fx max, wheel will Lock .i.e. if Brake Torque / R > X Fz, the wheel will lock.
Hence wheel locking tendency increases with 1) Less co-efficient of friction between road and Tyre (wet or icy roads, bald Tyres), 2) Less axle load (Rear wheels in Unladen condition)3) Higher brake torque (panic braking)
Normal force FZ
Lateral force FY
Normal force FZ
Longitudinal force FX
Tire
Braketorque
Direction of wheelrotation
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Consequences of Wheel lock
1) Substantial Reduction in braking force from the road, hence higher stopping distance
2) Reduction in Lateral stability, hence vehicle can spin out
3) Increased Tyre wear
It is not possible for a driver to continuously control individual wheel brake pressure precisely based on - Road condition & dynamic Load condition on each wheel.
ABS Function
To continuously detect impending wheel lock during braking and if wheel lock is foreseen, then to continuously modulate the brake pressure of that wheel to just avoid the
wheel lock.
Braking torque developed by the wheel corresponds to the maximum frictional
force that can be sustained by the tyre – road interface
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Facts to be Understood about ABS
• ABS does not apply the brake by itself, neither it can increase the magnitude of the brake intensity applied by the driver
• ABS does not come in to action unless there is a possibility of a wheel lock during braking
• ABS does not save the driver from reckless driving
• If ABS is not working due to a fault, the normal brake system continues to work in its full capacity.
• When ABS is not working on one wheel, the ABS of the opposite diagonal wheels will still function normally to provide partial benefits.
Additional Changes made in the brake circuit of 6X2 & 6X4 for ABS
• Brake split changes from X split to H split• Handbrake valve changed to more graduated
valve• Additional 15 litre Air tank fitted in the parking
brake circuit
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Typical ABS layout on a 4x2 Typical ABS layout on a 4x2 vehiclevehicle
1. ABS Modulator2. Wheel Speed Sensor3. Electronic Control Unit
1 1
1 1
ECU
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2
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2
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Typical ABS Schematic for 6X2 & 6X4 Vehicle
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Typical ABS System – Brake Schematic circuit with ABS
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ABS Working Process and components:
A Polewheel is fitted to the Rotating wheel hub on all four
wheels.
A Magnetic sensor is mounted on each wheel In close
proximity to the Polewheel,
The Sensor generates electrical pulses when the
Polewheel rotates.
The rate at which the pulses are generated is the measure
of each wheel speed.
This wheel speed signal is transferred to the Electronic
control unit (ECU)
When the wheel is about to lock, the ECU sends the signal
to the corresponding
Modulator Valve Solenoid, which releases pressure from
the Brake Chamber of that wheel brake. When the
Wheels recovers sufficiently pressure is re-applied again
by the ECU by switching
off the signal to the Modulator valve.
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ABS Components
•Pole wheel•Sensor•ECU•Modulator valves•ABS Wiring Harness (cables and connectors)•Blink code lamp and switch•Electrical Relays
Two Globally Renowned Supplier’s:•M/s Wabco Germany with M/s Sundaram
Clayton as an Indian Partner•M/s Knorr Bremse Germany represented by M/s Knorr Bremse India
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Pole wheel and sensor
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Functions of ABS components
Wheel Speed Sensors:Product Description:The wheel speed sensor is a magnetic sensor consists of a permanent magnet and coil assembly.
Function:It generates electrical pulses when the pole wheel rotates. The rate at which the pulses are generated (frequency) is a measure of the wheel speed.
Fitment:It is fitted with a special bush with spring clips to retain thesensor in position. The sensor pushed at the pole wheel by ~10 kg force so that optimum clearance is achieved after pole wheel rotation..
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Air Gap
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ak
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Incr
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peed
Magnetic type Version - L type or Straight type Generates sinusoidal voltage signal. The frequency of voltage generated is proportional to the wheel speed. The voltage signal is fed to the ECU for detecting the wheel lock
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Air gap between sensor and pole wheel to be maintained to 0.7 mm maximum
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•The amplitude of the signal, that is, the extent of the voltage induced,
• is influenced by the distance between the tone wheel and the sensor.
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Sensor and Pole wheel mounting on 109RR rear Axle
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Sensor fitment Photos on Rear Axle
Sensor
Axle Bracket
Mounting Bracket
Polewheel
Movie
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Sensor fitment Photos on Front Axle
PolewheelSensor
Movie
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Purpose : To modulate brake
chamber Pressure as per
electrical signal received from
ECU
Method of pressure modulation : By operating in three
states
Pressure Apply - Normal state
• Pressure Hold - Inlet solenoid energised
• Pressure release - Both Inlet & Exhaust
solenoid energised
Modulator Valve
Type : Twin Solenoid operated (Inlet, Exhaust) Normally open
Acts as pipe during normal brakingNo. of ports : 3 – Inlet , Delivery & ExhaustOperating voltage : 24V & 12V DC
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ABS Fitment – Modulator Valve – Front AxleABS Fitment – Modulator Valve – Front Axle
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Driver tips
Do what good drivers have always been doing;
Brake just the way you always have
Apply brakes as normal to stop in time.
Maintain pressure as required on your brake pedal while steering clear of any obstacles. During a brake application that could result in a wheel lock, ABS automatically releases and applies the brakes much faster than you could do with the brake pedal.
Always remember that you are the most important element in the safe operation of your vehicle
ABS is not an excuse to take unnecessary risks. Always drive carefully and stay a safe distance away from the vehicle in front of you.
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Driver tips
Safety aspect
ABS and other integrated functions improve safety, however it cannot extend performance beyond the limits of physics, e.g. it cannot prevent consequences related to tailgating ( excessive vehicle velocity in a curve)
System failure
Should a system failure occur the driver should continue to drive normally since normal brake function is guaranteed to full capacity.
ABS system failure should be corrected at the end of the trip.
Keep ABS working
Do not ignore the fault for a prolonged period. Keep the system fault free to ensure maximum safety.
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Body Builder precautions
Before modifying a bus, truck or motor home chassis equipped with ABS, review the following information. These tips will help you understand the ABS system and help avoid possible damage to that system when the chassis is altered.
1. Do not mount extreme heat sources (sources exceeding 85°C) near the ECU.These include cab heater, engine exhaust, etc.
2 Do not install RFI-emitting devices (such as radios, electric motors or pumps) on or near the ECU or other ABS components to help isolate the system from electrical interference.
3 Perform all chassis welding with all connections to the ECU disconnected.
4 When installing other components, be aware of and do not damage the ABS harness or connectors.
5 Do not cut or splice the ABS harness to provide power to other sources on the vehicle. Cutting or splicing the ABS harness may cause the system to malfunction.
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Body Builder precautions
6 When extending an OEM chassis, use the appropriate ABS harness extension cables and connectors.
7. All ground connections of the modulator assembly and ECU MUST have separate grounding points. We recommend that no other loads be connected to the grounds.
8. When painting or undercoating, make sure all connections are securely fastened.
9. Protect unfastened or exposed connectors.
10. Any ABS component removed during modification must be reinstalled as per OE specification
11. Before putting the vehicle into operation, perform the appropriate end of line test.
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ANTI-LOCK BRAKING SYSTEMANTI-LOCK BRAKING SYSTEM(ABS6)(ABS6)
DIAGNOSTICSDIAGNOSTICS
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ABS COMPONENTSABS COMPONENTS
ELECTRONIC CONTROL ELECTRONIC CONTROL UNIT (ECU)UNIT (ECU)
POLE WHEELPOLE WHEEL
WHEEL SPEED SENSOR WHEEL SPEED SENSOR (WSS)(WSS)
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CLAMPING SLEEVE CLAMPING SLEEVE (SENSOR BUSH)(SENSOR BUSH)
ABS COMPONENTSABS COMPONENTS
MODULATOR VALVE MODULATOR VALVE (MV OR PCV)(MV OR PCV)
X1 CONNECTOR OF X1 CONNECTOR OF POWER INTERFACE POWER INTERFACE HARNESSHARNESS(PIG TAIL HARNESS)(PIG TAIL HARNESS)
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ABS COMPONENTSABS COMPONENTS
MODULATOR VALVEMODULATOR VALVE CABLECABLE
X2 CONNECTOR OF X2 CONNECTOR OF FRAME HARNESS FRAME HARNESS ASSEMBLYASSEMBLY
SENSOR EXTENSION SENSOR EXTENSION CABLECABLE
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POLE WHEEL FAULT – DAMAGED OR POLE WHEEL FAULT – DAMAGED OR CONTAMINATED TOOTHCONTAMINATED TOOTH
Error Code: 2 – 3 – Front Axle Left Side (Steer Axle Left side) (A1L, FL or SL)
PRESS BLINK CODE SWITCH FOR 0.5 to 5 SECONDS AS SHOWN BELOW:
0.5s to 5 sec.
ON
OFF
COMPONENT
NUMBER2
FAULT TYPE
3
WARNING LAMP GLOWS (FLASHES AS SHOWN BELOW)
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31 2
ON
OFF
(0.5 to 5 s) + 1.0s
1.5s 1.5s
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POLE WHEEL FAULT – DAMAGED OR POLE WHEEL FAULT – DAMAGED OR CONTAMINATED TOOTHCONTAMINATED TOOTH
Error Code: 2 – 3 – Front Axle Left Side
DAMAGED TOOTH
CORRECT TOOTH
CONTAMINATED TOOTH
• If Pole Wheel run-out is observed – Replace Pole wheel
• Damaged Tooth - Replace Pole wheel
• Contaminated Tooth - Clean Pole wheel
Note:
If error persists, check for wheel bearing adjustment
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Error Code: 2 – 6 – Front Axle Left Side (Steer Axle Left side) (A1L, FL or SL)
USE A MULTIMETER AND CHECK FOR RESISTANCE BETWEEN PINS 5 & 8 OF X2 CONNECTOR
RESISTANCE > 1925 OHMS
USE A MULTIMETER AND CHECK RESISTANCE BETWEEN PINS OF SENSOR CONNECTOR
YES
NO
REPLACE WITH NEW SENSOR
RESISTANCE > 1925 OHMS
REPLACE SENSOR EXTENSION CABLE
SENSOR FAULT – SHORT OR BROKEN WIRESENSOR FAULT – SHORT OR BROKEN WIRE
SENSOR BROKEN SENSOR BROKEN WIREWIRE
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Error Code: 2 – 6 – Front Axle Left Side (Steer Axle Left side) (A1L, FL or SL)
SENSOR FAULT – SHORT OR BROKEN WIRESENSOR FAULT – SHORT OR BROKEN WIRE
• TURN ON IGNITION & CLEAR ERROR FROM THE ERROR MEMORY• TURN OFF AND ON THE IGNITION AGAIN• ONCE VEHICLE IS READY, DRIVE THE VEHICLE AT A SPEED OF ABOUT 10 - 15 KMPH• CONFIRM WARNING LAMP GOES OFF AUTOMATICALLY
AFTER RECTIFICATION OF ANY SENSOR FAULT, FOLLOW THESE STEPS:
TURN OFF THE IGNITION BEFORE CARRYING OUT ANY RECTIFICATION
SUCH AS REPLACING SENSOR OR SENSOR EXTENSION CABLE
NOTE:
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SENSOR FAULT – AIR GAP TOO LARGESENSOR FAULT – AIR GAP TOO LARGE
LARGE AIR GAP BETWEEN POLE WHEEL AND SENSOR ( AC Voltage < 100 mV)
Error Code: 4 – 1 – Rear Axle Left Side (Drive Axle Left side) (A2L, RL or DL)
• TURN OFF THE IGNITION
• PUSH THE SENSOR TILL IT BUTS WITH THE POLE WHEEL, USING A TOOL (TOOL SHALL NOT HAVE ANY SHARP EDGE)
• ROTATE THE HUB MANUALLY
• TURN ON IGNITION & CLEAR ERROR FROM THE ERROR MEMORY
• TURN OFF AND ON THE IGNITION AGAIN
• ONCE VEHICLE IS READY, DRIVE THE VEHICLE AT A SPEED OF ABOUT 10 – 15 KMPH
• CONFIRM WARNING LAMP GOES OFF AUTOMATICALLY
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•IF AIR GAP ERROR REPEATS FREQUENTLY• IN THE SAME WHEEL,
CHECK AND RECTIFY • EXCESSIVE WHEEL BEARING RUNOUT• POLE WHEEL RUNOUT
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ABS ECU – READING CONFIGURATIONABS ECU – READING CONFIGURATION
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ABS ECU – READING CONFIGURATIONABS ECU – READING CONFIGURATION
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1) Blink Code• Blink code is the easiest method of ABS
diagnostics & can be used effectively in most of the failure cases.
• In this method, only required tool for diagnostics is Blink Code Chart.
• In case of any error in ABS, ABS warning lamp on dash board will glow so that driver will understand that there is some fault in ABS.
• To further understand exact fault, a blink code switch can be operated so that the warning lamp will flash in certain fashion. The number of flashings can be counted manually & based on this count actual fault can be located on blink code chart.
• After troubleshooting, error can be erased from ABS memory using blink code switch.
• For specific errors, after troubleshooting, the vehicle should be driven at a speed of 10 to 15 Kmph during when the ECU does dynamic diagnostics and puts OFF the WL if no error is present.
Diagnostics: MethodsDiagnostics: Methods
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Blink Code – To Clear Error from Blink Code – To Clear Error from MemoryMemory
To Erase errors from the memory• Press and hold the Blink Code Switch• Switch ON the Ignition• After approximately 3 seconds release the blink code
Notes:
• The ABS warning lamp will glow when the blink code switch is pressed, if the ignition is already switched ON, however the ECU error memory will NOT be erased.• If any Sensor related errors were erased from the ECU memory, then the ABS warning lamp will glow during subsequent turning ON of the Ignition and will remain ON until the vehicle is driven to a speed of 10-15 Kmph and no active errors are present in the system.
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2) PC Based Diagnostics• PC base diagnostics is more useful for troubleshooting in service workshops. • One can directly read error messages on PC screen & accordingly decide on further action – Trouble shooting guidelines are part of it.• Required equipments are Laptop with diagnostics software installed, interface module, interface cable & adapters for connection with ECU.• Multi-meter for checking sensors, Modulator Valve Solenoids, Voltages etc • We can read information like ECU manufacturing data, software version etc.• Vehicle wise data base for recording history can be generated & updated for future use.
Diagnostics: MethodsDiagnostics: Methods
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1) Ensuring correctness of entire ABS electrical wiring
2) Ensuring correctness of pneumatic connections
3) Ensuring proper electrical contacts of all devices in system
4) Ensuring proper operation of all ABS components
5) Ensure proper operation of entire ABS
• EOL for ABS is also recommended for Service:
1) Pole wheel tooth damages or run-out, if present can be detected.
2) To detect Sensor air gap developed during fitment of Wheel Hub.
3) To Confirm functioning of replaced Modulator Valve
4) To confirm correct wiring, In case of replacement of Harness Assembly
5) To Configure ECU, when ECU is replaced.
6) To confirm pneumatic connections to Modulator valve etc.
Need of EOL TestNeed of EOL Test
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• 3 years or 300,000 km – check the functionality of the system using
Diagnostics cum End Of Line test equipment. In the case of failure, the
defective part is to be replaced. There are no serviceable ABS
components in the system.
Note:• The electrical functionality of the ABS
components – Electronic
Control Unit, modulators, sensors and cabling – is checked
automatically by in-built self diagnostic software and the driver is
warned of any malfunction or failure.
• Sensor Clamping Sleeve along with Sensor
Grease is available as a spares kit –For use
whenever Sensor is replaced.
Service Intervals:Service Intervals:
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Typical Field Problems on ABS:
Sensor Air Gap too Large
Sensor Short / Broken Wire
Modulator Valve Short / Broken Wire
Polewheel Damage / Sensor defective signal
Wrong Cable Connection of Modulator & Sensor – FL X FR interchange
Battery Over voltage / Under Voltage
ABS Warning Lamp blown
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Do’s: Use only approved grease (WABCO SPECIAL) to the sensor
DO’S AND DON’TS DURING ABS INSTALLATION
Sensor Installation
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Do’s: Always insert the Bush until its lug touches the bracket
DO’S AND DON’TS DURING ABS INSTALLATION
Sensor Installation
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Do’s: Protect the sensor cable with Corrugated sleeve
Warning ! “ Terminate the corrugated sleeve at foundation brake assembly entry point”
DO’S AND DON’TS DURING ABS INSTALLATION
Sensor Installation
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< 0.2 mm
Wheel Speed Sensor
Pole wheel
Note: Always push the sensor until it touches the pole wheel (Air gap < 0.2mm)
DO’S AND DON’TS DURING ABS INSTALLATION
Sensor Installation
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Note: Mount the modulator valve in the Chassis member with exhaust port facing the ground
Exhaust port
Inlet port
Delivery port
DO’S AND DON’TS DURING ABS INSTALLATION
Modulator valve Installation
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Note: Connect DBV delivery to Port 1 of MV and Port 2 of MV to Brake Chamber or spring brake actuator
DO’S AND DON’TS DURING ABS INSTALLATION
Modulator Valve Installation
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DO’S AND DON’TS DURING ABS INSTALLATION
Cable routing
Note : Clip the cable firmly
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DO’S AND DON’TS DURING ABS INSTALLATION
Cable routing
Warning ! Do not over tighten (Will cause damage to the cable inner leads )
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DO’S AND DON’TS DURING ABS INSTALLATION
Warning ! Remove vehicle battery connection and ECU connectors while doing any welding work in the vehicle
Vehicle service related
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DO’S AND DON’TS DURING ABS INSTALLATION
Warning ! Protect the Valve hoses / cables / extension cable while welding in the vehicle.
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Installation Demonstration on the vehicle
• Showing installation locations in the vehicle• Installation and dismantling Demonstration and Tips
(SCL ABS data.pdf)• Sensor
• Modulator
• ECU
• Cables
• Connectors
• Blink code lamp and button
• Instructions for covering the ECU before transporting the cowl (SCL ABS dat.pdf)
• Instructions for ECU location in the Bus • Instructions for bus body builders and cab builders (SCL
ABS data.pdf)
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ABS component Installation Demonstration
Sensor Installation• Pole wheel fitment
• Hub machining• Pole wheel checking for damaged tooth etc.,• Heating polewheel for 1 hr at 180 C deg• Ensure pole wheel is facing upward while placing hub on
ground • Press fitting pole wheel on hub fully • Always ensure correct seating of pole wheel on hub
collar• Check axial run-out of the pole wheel and ensure it within
0.1 mm • Sensor insertion with bush and grease – use only
approved grease (Staburags NPU 30 PTM of Kluber) • Push sensor bush fully in first and then insert the
sensor.• Check the seating of Sensor bush lugs in the bracket• Sensor cable routing – protect the sensor cable with
corrugated tube• Possibly route it along with brake hose by tying it to
hose with cable tie• Air gap setting by pushing the sensor to touch the
polewheel by special tool provided for pushing the sensor
• Do not hit or strike the sensor or push it with sharp edge
• Rear axle Sensor extension cable to pass through a grommet while coming out from a brake torque plate
• Do not pull the sensor cable as it can easily get damaged.
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ABS component Installation Demonstration (…. Contd)
Modulator Valve fitment • Ensure same make and voltage as that of ECU.• Exhaust facing downwards • Connect MV Inlet to DBV outlet and MV delivery to
SBA/BC – do not swap • Length of pipe + hose from MV delivery to SBA/BC
– less than 1.5 m• Fit the electrical connector properly.• Ensure that RH modulator valve is connected to RH
wheel chamber / actuator only.• Steer the front wheels to maximum positions and
verify that there is no rubbing of MV delivery hose with the Tyres.
ECU fitment • Vertical position• Away from heat sources• Location of ECU – protection against water
splashing• Connectors facig downward• Proper grounding to be provided.• For transporting the cowl, cover the ECU with
watertight plastic cover to prevent water entry.• All ground connections of the modulator assembly
and ECU must have • Separate grounding points. It is recommended to
connect no other loads to the ground.
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ABS component Installation Demonstration (…. Contd)
Cable routing • Cables to be covered with corrugated tubes• Cable ties to put at equal intervals• Clip the cables firmly - Over tightening of cables to
be avoided• All frame harness cables to be routed along long
member/ cross member.• ABS ground connections to be isolated from all
other grounds• Power to ECU through ignition key• Power to valves through ECU• Warning lamp and blink code switch are integrated
in the dash board • Fuse, retarder relay and diagnostic connector are
mounted inside the cabin
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ABS component Installation Demonstration (…. Contd)
General installation guidelines• Always block vehicle wheels during installation
/service• Stop engine when working under a vehicle• Support vehicle with rigid structure only • Ensure the battery connections are disconnected • Wind off spring brake actuator fully • Deplete the compressed air fully• Remove battery connections, ECU connector
and protect the valve hoses, cables and extension cables while doing welding work on vehicle