Lexus SC300 / Lexus SC400. Service manual — part 270

OK

NG

OK

NG

INSPECTION PROCEDURE

1

Check voltage between terminal 1 of R/B No. 6 (for TRAC motor relay) and body ground.

C

OK

P

Remove TRAC motor relay from R/B No. 6.

Measure voltage between terminal 1 of
R/B No. 6 (for TRAC motor relay) and body ground.

Voltage:

10 – 14 V

Check and repair harness or connector.

2

Check continuity between terminal 2 of R/B No. 6 (for TRAC motor relay) and terminal MTT of
ABS & TRAC ECU.

C

OK

Hint

Check continuity between terminal 2 or R/B No. 6 (for
TRAC motor relay) and terminal MTT of ABS & TRAC
ECU.

Continuity

There is a resistance of 4 – 6

between terminals BTM

and MTT of TRAC pump motor.

Repair or replace harness or TRAC pump motor.

BR–108

–

BRAKE SYSTEM

ANTI–LOCK BRAKE SYSTEM (ABS)

OK

NG

OK

NG

3

Check TRAC motor relay.

C

OK

P

OK

C

Remove motor relay from R/B No. 6.

Check continuity between each pair of terminal of motor
relay shown below.

1.

Apply battery voltage between terminals 3 and 4.

2.

Check continuity between terminals shown below.

Replace TRAC motor relay.

4

Check for open and short in harness and connector between TRAC motor relay and ABS &
TRAC ECU (See page

IN–33

).

Repair or replace harness or connector.

If the same code is still output after the diagnostic trouble code is deleted, check the contact condition
of each connection.
If the connections are normal, the ECU may be defective.

–

BRAKE SYSTEM

ANTI–LOCK BRAKE SYSTEM (ABS)

BR–109

DTC

21, 22,

23, 24

ABS Actuator Solenoid Circuit

CIRCUIT DESCRIPTION

This solenoid goes on when signals are received from the ECU and controls the pressure acting on the wheel
cylinders, thus controlling the braking force.

DTC No.

DTC Detecting Condition

Trouble Area

21

Conditions (1) through (3) continue for0.05 sec. or more:

(1) ABS solenoid relay (SR) terminalvoltage: Battery positive

voltage

(2) Voltage of ABS (& TRAC) ECU terminal AST: Battery posi-

tive voltage

(3) When power transistor of ECU is ON,voltage of terminal

SFR is 0 V or batterypositive voltage.

ABS actuator

Open or short in SFR circuit.

ECU

22

Conditions (1) through (3) continue for0.05 sec. or more:

(1) ABS solenoid relay (SR) terminalvoltage: Battery positive

voltage

(2) Voltage of ABS (& TRAC) ECU terminal AST: Battery posi-

tive voltage

(3) When power transistor of ECU is ON,voltage of terminal

SFL is 0 V or batterypositive voltage.

ABS actuator

Open or short in SFL circuit.

ECU

23

Conditions (1) through (3) continue for0.05 sec. or more:

(1) ABS solenoid relay (SR) terminalvoltage: Battery positive

voltage

(2) Voltage of ABS (& TRAC) ECU terminal AST: Battery posi-

tive voltage

(3) When power transistor of ECU is ON,voltage of terminal

SRR is 0 V or batterypositive voltage.

ABS actuator

Open or short in SRR circuit

ECU

24

(Only ve-

hicles with

TRAC)

Conditions (1) through (3) continue for0.05 sec. or more:

(1) ABS solenoid relay (SR) terminalvoltage: Battery positive

voltage

(2) Voltage of ABS & TRAC ECU terminal AST: Battery posi-

tive voltage

(3) When power transistor of ECU is ON,voltage of terminal

SRL is 0 V or batterypositive voltage.

ABS actuator

Open or short in SRL circuit.

ECU

Fail safe function:

If trouble occurs in the actuator solenoid circuit, the ECU cuts off current to the

solenoid relay and prohibits ABS control.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

BR–110

–

BRAKE SYSTEM

ANTI–LOCK BRAKE SYSTEM (ABS)

WIRING DIAGRAM

–

BRAKE SYSTEM

ANTI–LOCK BRAKE SYSTEM (ABS)

BR–111