service handout

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Service Training HANDOUTService Training HANDOUTON ON

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

3

2

22

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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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)


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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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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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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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


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”


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)


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


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


Modulator Valve Installation

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Cable routing

Note : Clip the cable firmly

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Cable routing

Warning ! Do not over tighten (Will cause damage to the cable inner leads )

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Warning ! Remove vehicle battery connection and ECU connectors while doing any welding work in the vehicle

Vehicle service related

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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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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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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

service handout

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