HỆ THỐNG PHANH CHỐNG bó CỨNG ABS TRÊN XE KHÁCH

1.2 Operation Antilock Brake System A.B.S automatically adjusts air pressure to the brake, if over braked, to prevent wheel lock up and to optimize utilization of available traction.. T

Anti-Lock Brake System

Hyundai Commercial Vehicles

Published by Chonan Technical Service Training Center

Foreword

This training guide has been published to help all the service personnel of HYUNDAI distributors, authorized HYUNDAI workshops and commercial vehicle fleet companies be familiar with the electrical system of HYUNDAI vehicles

The applicable vehicles are all kinds of Hyundai Truck and Bus

All the contents of this guide, including, drawings and specifications are the latest available at the time of publication

All the contents of this guide will be helpful when you provide efficient and correct service on electrical system

For detailed service specifications and service procedures, please refer to the relevant shop manuals.ⓒ2003 Hyundai Motor Company

Chonan Technical Service Training Center

All rights reserved This publication may not be reproduced in whole or in part without the written consent of HMC

Contents

1 General ··· 7

1.1 Characteristics ··· 7

1.2 Operation ··· 7

1.3 ASR ··· 10

1.4 ABS Control Cycle ··· 10

1.5 Cautions ··· 12

2 HD 65,72 Truck and County Bus ··· 13

2.1 General ··· 13

2.2 System Components ··· 14

2.3 Wheel Speed Sensor ··· 15

2.4 Modulator and Relay ··· 16

2.5 Hydraulic Circuit ··· 17

2.6 ABS Control Module ··· 19

2.7 Control Logic ··· 20

2.8 Diagnosis ··· 20

2.9 Fault Codes ··· 21

2.10 Service Data ··· 22

2.11 Cautions ··· 24

2.12 Wiring Diagram ··· 25

2.13 Troubleshooting ··· 26

3 Medium and Heavy Duty Truck ··· 29

3.1 System Layout ··· 29

3.2 ABS Control Module ··· 31

3.3 Wheel Speed Sensor ··· 33

3.4 Pressure Control Valve ··· 35

3.5 Fault Codes ··· 37

3.6 Wiring Diagram ··· 43

4 Aero Bus ··· 44

4.1 System Layout ··· 44

4.2 ABS Electronic Control Unit ··· 47

4.3 Wheel Speed Sensor ··· 50

4.4 Pressure Modulator Valve ··· 51

4.5 Anti Spin Regulator ··· 53

4.6 Diagnosis ··· 54

4.7 Wiring Diagram ··· 57

1 General

1.1 Characteristics

Under repair braking or slippery road condition by rain or snow, braking a vehicle in running is apt to generate skid condition The skid may decrease braking force to increase braking distance, generate spin by traverse slipping, and or disable steering control, resulting

to an accident Therefore the ABS system is designed to prevent from wheel locking and slip upon braking for ensuring :

1.1.3 Optimum stopping distance

A.B.S provides optimum-stopping distance by reducing the slip caused by wheel locking and ensures better stopping ability

1.2 Operation

Antilock Brake System (A.B.S) automatically adjusts air pressure to the brake, if over braked, to prevent wheel lock up and to optimize utilization of available traction By preventing wheel lock up while braking, ABS ensures the vehicle remains steerable and stable By optimization of the available traction, ABS can reduce stopping distances

When ABS is installed, an Anti Spin Regulation (ASR) can also be installed ASR automatically prevents spinning of drive wheel when starting upon accelerating ASR also transfers drive torque to the wheel with the greatest traction

The Anti-lock Brake System consists of the following components:

▶ Wheel speed sensor

▶ Electronic Control Module (ECM)

▶ Pressure Modulator

▶ ABS warning lamp

▶ ABS diagnostic lamp / wheel slip indicator

▶ ASR valve (if equipped)

1.2.1 ABS Operating PrincipleIf the driver applies the brakes too hard, the wheel will begin

adjust the brake pressure to the appropriate wheel to prevent wheel lock and achieve optimum adhesion The brake pressure is controlled by the Pressure Control Valves (PCV), which can reduce, hold or increase air pressure (up to pressure applied by the driver) in precise increments

The ABS is not activated unless the wheels show a tendency to lock during braking In the event of an ABS will shut off the affected part of the system and will urn on the ABS warning lamp The part of the ABS which is shut off will revert to conventional non – ABS braking

1.2.2 ASR operating principle

Under adverse conditions the drive wheels may slip while attempting to drive away or accelerate If traction is different on both sides of the vehicle, the wheel with the lowest traction may slip and in many cases the vehicle may not be able to move

The ASR (traction control) system can remedy this situation by braking the slipping wheel through the use of the ASR solenoid valve and the ABS pressure control valves The drive torque is then transferred to the wheel with traction allowing the vehicle to drive away In this manner ASR acts as an automatic differential lock

1.2.3 Slip rate(λ)Upon braking a vehicle, which is running, slip rate changes from 0 to 100%

until the wheel are locked and the vehicle stops completely The slip rate λ may be indicated

as the below :

λ = (A-B / A) ×100(%)

A=Vehicle speed

B=Wheel speed

Anti-Lock Brake System

Chonan Technical Service Training Center

6

ABS Operating Principle

If the driver applies the brakes too hard, the wheel will begin to lock By monitoring the

wheel speeds, the ABS Electronic Control Module (ECM) will determine when locking is

about to occur When a specified difference wheel speed vs.vehicle speed is reached and one or more wheels show a tendency to lock, the ECM will adjust the brake pressure to

the appropriate wheel to prevent wheel lock and achieve optimum adhesion The brake

pressure is controlled by the Pressure Control Valves (PCV) which can reduce, hold or

increase air pressure (up to pressure applied by the driver) in precise increments

The ABS is not activated unless the wheels show a tendency to lock during braking In the event of an ABS will shut off the affected part of the system and will urn on the ABS

warning lamp The part of the ABS which is shut off will revert to conventional non – ABS braking

ASR operating principle Brake control ASR

Under adverse conditions the drive wheels may slip while attempting to drive away or

accelerate

If traction is different on both sides of the vehicle,the wheel with the lowest traction may

slip and in many cases the vehicle may not be able to move

The ASR(traction control) system can remedy this situation by braking the slipping wheel through the use of the ASR solenoid valve and the ABS pressure control valves The drive torque is then transferred to the wheel with traction allowing the vehicle to drive away In this manner ASR acts as an automatic differential lock

Brake slip()0.2

1.00.80.60.4

The slip rate(λ) and the surface friction coefficient(μB) may be correlated as the illustration The slip rate(λ) at the max μB differs by the road condition but the max range is approx,8∼30% The cornering force (transversely slip preventing force) decreases with increasing slip late Once wheel are locked, surface friction coefficient decreases and slip friction coefficient becomes to “0”, and then wheels are easy to slip

In fact locked rear wheels generate spinning and locked front wheels disables steerability The ABS system controls braking force to maintain the slip rate in the range of 8 ∼30%, in order to generate maximum surface friction coefficient, control slip friction coefficient at higher range, and provide stability and steerability

1.2.4 ABS Effect

The ABS system provides stable braking under extreme condition Even braking rapidly

on frozen or snowy road, wheels are not locked and maintain max friction with the road surface to provide optimum braking distance Restricting the pressure in the chamber locked

at the wheel side on the road surface, the system ensures straightforward motion The driver may acquire correct alignment of the vehicle by adjusting the steering wheel only a little

When one side wheel is caught at slippery road or muddy surface, the slipping wheel idles, that the vehicle is hard to run and power train (differential, axle shaft) In order to compensate idling for stability, the ASR, feature controls to brake the idling wheel properly and transfer the rotating force to the other wheel to enable launching The ASR feature is traction control, and an extensive application of the ABS system Only ASR control valves (solenoid valves) integrated on the ABS system to make the ASR feature

1.3.1 ASR Effect

Upon starting or accelerating the vehicle, a wheel may idle on a slippery road surface or

so Then the vehicle may not start or may be unstable to incur accident When speeds of both side wheels are different, the ASR system brakes operate to the faster wheel (idling wheel) to make the both wheels speed same The system does not operate at or above 30km/h

1 Starting at a surface of which one side is frozen (ex : bus stop) or accelerating or starting at a cornering range, the system provides optimum drivability

2 Idling wheels as well as locked wheels do not transfer driving force, to decrease steerability and put the rearmost part of the vehicle out of track The ASR system maintains the vehicle under control

3 The system decreases wear or driving mechanism (differential, axle) and tires

1.4 ABS Control Cycle

The figure below shows, in principle, an example of a control cycle with the most important control variables, wheel deceleration threshold –b, wheel acceleration threshold +b and slip thresholds Lambda 1 and Lambda 2

If the brake pressure increases, the wheel is progressively decelerated At point 1 wheel deceleration exceeds a value that cannot physically be reached by vehicle deceleration The reference speed and the wheel speed, which up to this Point had been the same, now diverge until at point 2 the wheel speed has

achieved a high deceleration A maximum value is derived from the reference speeds of the wheels of a diagonal and of the other front wheel speed, is then generally used as a common reference speed for all three wheels of this diagonal Wheel slip is calculated from actual wheel speed (i.e sensor output) and the corresponding reference speed

The deceleration threshold –b is exceeded at point 2 The wheel now moves into the unstable region of the ц-λ slip curve at which point the wheel has reached its maximum braking force and any further increase in braking torque increase only the rate at which the wheel decelerates For this reason brake pressure is quickly reduced and so wheel deceleration decreases

The time taken for wheel deceleration is determined by the hysteresis of the wheel brake and by the characteristic of the ц-λ slip curve in the unstable region Only after wheel brake hysteresis has been overcome does a continued reduction in pressure lead to a decrease in wheel deceleration At point 3 the deceleration signal – b drops below the threshold and the brake pressure is held at a constant level for a set time T1

Normally, wheel acceleration will exceed the acceleration threshold +b within this set time (point 4) So long as this threshold is exceeded, brake pressure is kept constant If (for example on a low friction surface) the +b signal is not generated within time T1, brake pressure is further decreased by slip signal Lambda 1 During this control phase the higher slip threshold Lambda 2 is not reached After falling below the threshold at point 5 the +b signal drops The wheel is now in the stable region of the ц-λ slip curve and the ц- value is

a bit below the maximum

Brake pressure is now rapidly applied for time T2 to overcome brake hysteresis The time T2 is fixed for the first control cycle and then calculated new for each subsequent control phase After the initial rapid phase, brake pressure is then increased more gradually by

“pulses”, by alternating pressure hold and pressure increase The basic logic demonstrated in this example is not fixed at all; it rather adapts to the corresponding dynamic response of the wheel to varying coefficients of friction, i.e it implements an adaptive system control All threshold values depend on several different parameters as for instance the driving speed and the vehicle deceleration etc

The number of control cycles results from the dynamic response of the overall control system composed of the ABS – control - the wheel – the road Here, the frictional connection

1.5 CautionsUpon Ignition on, the ABS warning lamp (red) shall be on and go out at

10km/hbor more after starting the vehicle

2 Braking normally on a normal road surface, the driver is hard to feel the ABS effect The ABS effect is designed to feel at braking on a certain surface that wheels are apt

to be locked as slippery road-frozen, snowy, rainy road

Note

On rapid braking or braking on a slippery road, do not pump the brake pedal as a ABS vehicle Press the pedal properly depending on situation (hard or light) at once and continuously for optimum ABS effect

non-3 ABS vehicle an integration of the ABS system on a non-ABS vehicle The basic braking system shall be maintained properly, and the ABS system cannot improve the serviceability.Optimum ABS effect regularly put the wheel speed sensors to bottom into the pulse ring Upon removing the hub and drum assembly to replace the lining/clean off dirt (lining, particles, dust, oil etc) on the speed sensor

-40∼120℃

Operating Temp Range

200 kg/㎠(max 250 kg/㎠) Operating Pressure

0.65 ±0.01mm Air Gap

24 V Operating Voltage

Warning Lamp

2.6 kg Weight

Hydraulic

Modulator

120mV(at 2.75km/h) Minimum output

1600±10% Ω Resistance

2.2 System Components

The Anti-lock Brake System (ABS) controls the hydraulic brake pressure of all four gear wheels during sudden braking and braking on hazardous road surfaces, preventing the wheels from locking This ABS provides the following benefits

1) Enables steering around obstacles with a greater degree of certainty even during panic braking

2) Enables stopping during panic braking while allowing stability and steerability to a minimum, even on curves

In case a malfunction occurs, a diagnosis function and fail-safe system have been included for serviceability

2.3 Wheel Speed Sensor

2.3.1 Disk type

2.3.2 Drum Type

2.4 Modulator and Relay

Note

1 Never attempt to disassemble the ABS modulator

2 The modulator must be transported and stored in upright position and with sealed ports The modulator must not be drained

2.4.1 Removal and Installation

Removal

1 Disconnect motor pump and relay box harness and remove the ABS relay box mounting nuts

2 Remove the relay box from relay box mounting

3 Disconnect the brake tubes from the ABS modulator

4 Remove the ABS modulator mounting bolts

Modulator Valve Relay (5P) Pump Motor Relay (4P)

Relay Box

2 Tighten the modulator mounting bolts and brake tube nuts to the specified torque

3 Bleed the brake system

Modulator mounting nut : 12-19 lb.ft (1.7-2.6 kgf.m)

Brake tube nut : 9-12 lb.ft (1.2-1.7 kgf.m)

2.5 Hydraulic Circuit

Relay box

Mounting nut

Tube nut

2.5.1 Normal Mode

2.5.2 Hold Mode

2.5.3 Dump Mode

2.5.4 Increase Mode

2.6 ABS Control Module

2.6.1 ABSCM Connector Configuration (Component Side)

1 Ignition “ON” 13 Front right wheel speed sensor(+)

5 Front left inlet solenoid valve 14 Front right wheel speed sensor(-)

6 Rear right inlet solenoid valve 16 Data link connector

7 ABS relay control 25 Rear left outlet solenoid valve

9 Front left wheel speed sensor (+) 26 Front right outlet solenoid valve

10 Front left wheel speed sensor (-) 28 Ground

11 Rear right wheel speed sensor (+) 29 Ground

12 Rear right wheel speed sensor (-) 30 Ground

Pin Plug Assignment Pin Plug Assignment

31 ABS indicator control 45 ABS relay control

33 Front left outlet solenoid valve 46 Data link connector

34 Rear right outlet solenoid valve 49 Pump motor monitor

35 ABS relay control 53 Rear left inlet solenoid valve

37 ABS relay control 54 Front right inlet solenoid valve

39 Rear left wheel speed sensor(+) 55 Ground

40 Rear left wheel speed sensor(-)

2.6.2 Modulator Connector Configuration (Harness Side)

Plug Assignment

Front left inlet valve ground

Rear right Inlet valve ground

Front right Inlet valve ground

Rear left Inlet valve ground

EB

Exhaust Brake Cut Relay

2.8 Diagnosis

2.8.1 Conditions of warning lamp ON

1 2 seconds after IG switch “ON”

2 System Fails

3 During self-diagnosis

4 Disconnecting the ECU connector

Note

ABS warning lamp should be turned-off when driving the vehicle

2.8.2 System diagnosis step

The ABSCM continuously checks the state of the electrical integrity of ABS and if detects

a failure, it inform the fault codes in SRI lamp flash code

2.8.3 SRI code check

With ABS check switch turned ON and the ignition switch turned ON, diagnostic trouble code can be checked, if faults are detected, with the reading of SRI lamp flash

1 Ground pin 6 of diagnosis connector as shown in

the figure

2 Turn the ignition switch ON

3 SRI lamp will be illuminated for 2 seconds and

then read the following Diagnostic trouble code

4 First digit of Diagnostic trouble code is determined

by the number of long flashes (1.5sec) and after

the following 2 seconds brake second digit is

determined by the number of short flashes (0.5sec)

5 Once the SRI lamp flashing is completed Next active trouble code or history trouble code stored at ABSCM will be followed after 3sec brake while the “L” terminal is shorted to ground or the ignition switch is ON

6 Diagnosis Trouble code will be retained in the ABSCM until the ignition has been switched ON and the vehicle speed exceeded 10km/h 20 times

ABS Service reminder indicator

2.9 Fault Codes

Fault Codes Description

21 Front right wheel speed sensor short

11 Front right wheel speed sensor open

22 Front left wheel speed sensor short

12 Front left wheel speed sensor open

23 Rear right wheel speed sensor short

13 Rear right wheel speed sensor open

24 Rear left wheel speed sensor short

14 Rear left wheel speed sensor open

15 Wheel speed sensor (Teeth number malfunction)

41 Front right inlet valve malfunction

45 Front right outlet valve malfunction

42 Front left inlet valve malfunction

46 Front left outlet valve malfunction

43 Rear right inlet valve malfunction

47 Rear right outlet valve malfunction

44 Rear left inlet valve malfunction

48 Rear left outlet valve malfunction

51 Valve relay malfunction

53 Pump motor malfunction

16 Voltage out of range

38 Brake lamp switch malfunction

35 Exhaust brake malfunction

2.10 Service Data

ECU – ABS Connector (Wiring side connector)

9+10 13+14 39+40 11+12

5+(-) 54+(-) 53+(-) 6+(-)

25.6±0.5 25.6±0.5 25.6±0.5 25.6±0.5

33+(-) 26+(-) 25+(-) 34+(-)

18.3±0.5 18.3±0.5 18.3±0.5 18.3±0.5

Modulator Connector (Modulator side connector)

25.6±0.5 25.6±0.5 25.6±0.5 25.6±0.5

18.3±0.25 18.3±0.25 18.3±0.25 18.3±0.25

8 10 2

Modulator Connector (Modulator side connector)

Relay box

connector

Valve relay

Valve relay excitations terminal

2+6 103 ± 10 Ω

Supply B+

to terminal

No 10 (at 23℃) Valve relay

switch terminal (NO)

Ω

Valve relay switch terminal (NC)

Motor Relay

Valve relay excitations terminal

2+11 80 ± 8 Ω

at 23℃

Valve relay switch terminal (NO)

Internal circuit

to terminal

No 10

2.11 Cautions

1) Be careful to shock and don’t spray water to ECU

2) Do not remove and/or rework wiring or connector at ignition switch ON

3) Do not remove battery terminal while engine is running

4) Tighten all of bolt (ground,etc) with specified torque after removing all of dirties

5) Charge the battery after removing it from the vehicle

6) Turn-off the all of switch and remove the battery (-) terminal before welding

ELECTRONIC CONTROL UNIT(24V)

86 85 30

- Interfered sensor wire

- Malfunction of sensor coil

- Improper air gap

- Abnormal ABS control

- Other wheels are normal

- System shut off after ABS event

- Visual check for wiring

- Check resistance of sensor

- Check air gap

22

Front left wheel speed sensor short

23

Rear right wheel speed sensor short

24

Rear left wheel speed sensor short

11

Front right wheel speed sensor open

- Disconnected sensor connector

- Cut sensor cable

or wire

- Cut sensor coil

- Abnormal ABS control

- Other wheels are normal

- System shut off after ABS event

- Check connection of sensor

- Visual check for sensor cable or wire

- Check sensor resistance

12

Front left wheel speed sensor open

13

Rear right wheel speed sensor open

14

Rear left wheel speed sensor open

15

Wheel speed sensor

malfunction

- Cut sensor cable

or wire

- Malfunction of sensor coil

- Improper air gap

- Abnormal ABS control

- System shut off when non ABS control

41

Malfunction of front right inlet valve - Disconnected

connector

- Malfunction of sensor coil

- Blown fuse (15A)

- Malfunction of

- Abnormal ABS control

- System shut off

- Check improper installation for valve relay and modulator connector

- Check resistance for

42

Malfunction of front left inlet valve

Malfunction of

Trouble

Code Trouble Parts Probable Cause Symptom Repair Instruction

44

Malfunction of rear left inlet valve

- Disconnected connector

- Malfunction of sensor coil

- Blown fuse (15A)

- Malfunction of valve relay

- Abnormal ABS control

- System shut off

- Check improper installation for valve relay and modulator connector

- Check resistance for valve relay

- Check fuse

45

Malfunction of front right outlet valve

46

Malfunction of front left outlet valve

47

Malfunction of rear right outlet valve

48

Malfunction of rear left outlet valve

51 Malfunction of

valve relay

- Disconnected valve relay connector

- Malfunction of valve relay

- Malfunction of wiring harness

- Unable to drive valve

- Shut off system

- Check improper connection

- Check ABS relay box

53 Malfunction of

pump/motor

- Disconnected pump/motor connector

- Bad ground contact

- Malfunction of relay

- Blown fuse (30A)

- Unusual dump mode control

- Shut off system

- Check improper connection

- Check ground point

- Check ABS relay box

- Check fusible link

- Warning lamp ON but system is not shut off

- Unable to control ABS while

warning lamp ON

- Check battery voltage

- Check alternator

- Unable to control ABS

- Shut off System

- Replace ABSCM

38

Malfunction of brake lamp switch

- Disconnected switch connector

- Cut brake lamp wire

- Warning lamp is

on

- System is not shut off

- Check brake lamp switch terminals

- Check brake lamp bulb

3 Medium and Heavy Duty Truck

3.1 System Layout

3.1.1 A.O.H Brake – 6  4 Dump Truck

1 Air Compressor 11 Air Master

2 Air Drier 12 Pressure Control Valve

4 4-circuit Protection Valve 14 Double Check Valve

6 Parking Brake Valve 16 Wheel Speed Sensor

7 Quick Release Valve 17 3-way Magnetic Valve

8 Remote Chamber 18 Exhaust Brake

9 Dual Brake Valve 19 Intake Silencer

3.1.2 Full Air Brake – 6  4 Tractor

1 Air Compressor 12 Wheel Speed Sensor

5 4-Circuit Protection Valve 16 Synchronizer Valve

6 Dual Brake Valve 17 Parking Brake Valve

7 3-Way Magnetic Valve 18 R-14 Valve

8 Exhaust Brake 19 Air Service Valve

9 Brake Chamber 20 Trailer Brake Valve

10 Pressure Modulator Valve 21 Spring/Brake Chamber

11 Quick Release Valve