The ABS consists of components such as the wheel
speed sensors, stoplight switch, hydraulic unit
assembly (integrated with ABS-ECU) and the ABS
warning light. If a problem occurs in the system, the
malfunctioning components can be identified and the
trouble symptoms will be memorized by the diagnos-
tic function.
The system has the EBD (Electronic Brake-force
Distribution) control system which provides the ideal
braking force for the rear wheels.
In addition, reading of diagnostic trouble codes and
data list and actuator testing are possible by using
the Scan Tool.

EBD CONTROL
In ABS, electronic control method is used whereby
the rear wheel brake hydraulic pressure during brak-
ing is regulated by rear wheel control solenoid valves
in accordance with the vehicle's rate of deceleration
and the front and rear wheel slippage which are cal-

culated from the signals received from the various
wheel sensors. EBD control is a control system
which provides a high level of control for both vehicle
braking force and vehicle stability. The system has
the following features:

• Because the system provides the optimum rear

wheel braking force regardless of the vehicle
laden condition and the condition of the road sur-
face, the system reduces the required pedal
depression force, particularly when the vehicle is
heavily laden or driving on road surfaces with
high frictional coefficients.

• Because the duty placed on the front brakes has

been reduced, the increases in pad temperature
can be controlled during front brakes applying to
improve the wear resistance characteristics of the
pad.

• Control valves such as the proportioning valve

are no longer required.

CONSTRUCTION DIAGRAM

ITEM

SPECIFICATION

ABS type

4-sensor, 3-channel type

Speed sensor

Magnet coil type on 4-wheels

Front ABS rotor teeth

Rear ABS rotor teeth

AC309306

ABS RELAY

HYDRAULIC UNIT (INTEGRATED

WITH ABS-ECU)

DATA LINK CONNECTOR

STOPLIGHT SWITCH

ABS ROTOR

WHEEL SPEED SENSOR

ABS WARNING LIGHT

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

TSB Revision

ANTI-LOCK BRAKING SYSTEM (ABS) <RWD>

35B-3

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

INTRODUCTION TO ANTI-LOCK BRAKING SYSTEM DIAGNOSIS

M1352012500415

The anti-lock braking system (ABS) operates differ-
ently from conventional brake systems. These differ-
ences include sounds, sensations, and vehicle
performance that owners and service technicians
who are not familiar with ABS may not be used to.
Some operational characteristics may seem to be
malfunctions, but they are simply signs of normal
ABS operation. When diagnosing the ABS system,
keep these operational characteristics in mind.
Inform the owner of the kind of performance charac-
teristics to expect from an ABS-equipped vehicle.

System Check Sound

When starting the engine, a thudding sound can
sometimes be heard coming from the engine com-
partment. This is a normal sound during the ABS
self-check.

ABS Operation Sounds and Sensations

During normal operation, the ABS makes several
sounds that may seem unusual at first.

• A whining sound is caused by the ABS hydraulic

unit motor.

• When pressure is applied to the brake pedal, the

pulsation of the pedal causes a scraping sound.

• When the brakes are applied firmly, the ABS

operates, rapidly applying and releasing the
brakes many times per second. This repeated
application and release of braking forces can
cause the suspension to make a thumping sound
and the tires to squeak.

Long Stopping Distances on Loose Road
Surfaces

When braking on loose surfaces like snow-covered
or gravel roads, the stopping distance can be longer
for an ABS-equipped vehicle than the stopping dis-
tance for a vehicle with a conventional brake system.

Shock at Starting Check

Shock may be felt when the brake pedal is lightly
pressed while driving at a low speed. This is a nor-
mal characteristic because the ABS system opera-
tion check is carried out when vehicle speed is 8
km/h (5 mph) or less.

ABS Diagnostic Trouble Code Detection
Conditions

ABS diagnostic trouble codes (ABS DTCs) are set
under different conditions, depending on the mal-
function detected. Most ABS DTCs will only be set
during vehicle operation. Some ABS DTCs will also
be set during the ABS self-check immediately after
the engine is started.
When you check if an ABS DTC will be displayed
again after the DTC has been erased, you should
recreate the ABS DTC set conditions. Depending on
the detection timing and set conditions for the spe-
cific ABS DTC, you must either drive the vehicle or
turn the engine off and restart it. To set the proper
conditions for that DTC again, refer to "ABS DTC
SET CONDITIONS" for each ABS DTC that you are
trying to reset.

ANTI-LOCK BRAKING SYSTEM (ABS) DIAGNOSIS

TSB Revision

ANTI-LOCK BRAKING SYSTEM (ABS) <RWD>

35B-4

TROUBLESHOOTING STRATEGY

M1352011100588

Use these steps to plan your diagnostic strategy. If
you follow them carefully, you will be sure that you
have exhausted most of the possible ways to find an
ABS fault.
1. Gather information about the problem from the

customer.

2. Verify that the condition described by the

customer exists.

3. Check the vehicle for any ABS DTC.
4. If you cannot verify the condition and there are no

ABS DTCs, the malfunction is intermittent. Refer
to GROUP 00, How to use
Troubleshooting/Inspection Service Points

− How

to Cope with Intermittent Malfunctions

P.00-7

5. If you can verify the condition but there are no

ABS DTCs, or the system cannot communicate
with the scan tool, check that the basic brake
system is operating properly.

• If the basic brake system is not operating prop-

erly, refer to the GROUP 35A, Basic Brake Sys-
tem Diagnosis

P.35A-3

• If the basic brake system is operating properly,

refer to

P.35B-36

6. If there is an ABS DTC, record the number of the

DTC, then erase the DTC from the memory using
the scan tool.

7. Duplicate the ABS DTC set conditions to see if the

same ABS DTC will set again.

• If the same ABS DTC sets again, perform the

diagnostic procedures for the DTC. Refer to

P.35B-9

• If you cannot get the same ABS DTC to set

again, the malfunction is intermittent. Refer to
GROUP 00, How to use How to Cope with Inter-
mittent Malfunctions

P.00-7

DIAGNOSTIC FUNCTION

M1352011200734

HOW TO CONNECT THE SCAN TOOL (MUT-III)

Required Special Tools:

• MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: MUT-III USB Cable

• MB991911: MUT-III Main Harness B

CAUTION

To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
1. Ensure that the ignition switch is at the "LOCK" (OFF)

position.

2. Start up the personal computer.
3. Connect special tool MB991827 to special tool MB991824

and the personal computer.

4. Connect special tool MB991911 to special tool MB991824.
5. Connect special tool MB991911 to the data link connector.
6. Turn the power switch of special tool MB991824 to the "ON"

position.
NOTE: When the special tool MB991824 is energized, spe-
cial tool MB991824 indicator light will be illuminated in a
green color.

7. Start the MUT-Ill system on the personal computer.

NOTE: Disconnecting the scan tool MB991958 is the
reverse of the connecting sequence, making sure that the
ignition switch is at the "LOCK" (OFF) position.

AK303629AB

MB991911

MB991827

MB991824

16-PIN

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