1991 LEXUS SC400 brake

WIRING DIAGRAM
DTC51ABS Pump Motor Lock
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
51Pump motor is not operating normally duringinitial
check.
ABS pump motor
Fail safe function: If trouble occurs in the ABS pump motor, the ECU cuts off the current to the solenoid
relay and prohibits ABS control.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
See inspection of ABS pump motor (See page BR±65 or BR±68 ).
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±125
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IN±33
DTC53TRAC±Pump Motor Lock
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
53
TRAC pump motor is locked

Open for TRAC pump motor ground.

TRAC pump motor

Harness or connector between TRAC pump&
motor and body ground.

TRAC Actuator

ABS & TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±126±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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WIRING DIAGRAM
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±127
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OKNG
OKNG
INSPECTION PROCEDURES
1Check operation of TRAC pump & motor.
C
OK
P
Notice
Disconnect TRAC pump & motor connector.
Connect positive
lead to terminal 3 or TRAC pump &
motor connector and negative  lead to terminal 1.
Do not apply battery voltage for more than 3 sec.
The TRAC pump motor should emit an operating
sound.
Go to step 3.
2Check continuity between terminal 1 of TRAC pump & motor connector and b\
ody ground.
C
OK
Measure resistance between terminal 1 of TRAC pump
& motor connector and body ground.
Resistance: 0  (Continuity)
Repair or replace harness or connector.
Replace TRAC pump & motor.
BR±128±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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OKNG
NGOK
OKNG
3Check harness and connector between ABS & TRAC ECU and TRAC pump & motor (Se\
e page
IN±33).
Repair or replace harness or connector.
4Check voltage between terminals PR and E2 of ABS & TRAC ECU connector.
C
OK
P
OK
C
Notice
1. Remove ABS & TRAC ECU with connectors still
connected.
2. Operate the engine for about 30 seconds at idle speed to raise the pressure of the TRAC actuator
to a high level.
1. Stop the engine and then turn ignition switch ON.
2. Measure voltage between terminals PR and E2 of ABS & TRAC ECU connector.
Voltage: 4 ± 8 V
1. Drain the fluid out of the actuator to reduce the pres-
sure.
2. Measure voltage between terminal PR and E2 of ABS & TRAC ECU connector.
Voltage: 10 ± 14 V
Add fluid to reservoir after the check.
Check and replace ABS & TRAC ECU.
5Check harness and connector between ABS & TRAC ECU and TRAC actuator (See page IN±33).
Repair or replace harness or connector.
Replace TRAC actuator.
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±129
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BR±228
WIRING DIAGRAM
DTC54Excessive Operation of TRAC Pump Motor
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
54
TRAC motor relay ON is output continuously10 times
at intervals of less than 24 sec.when traction control is
not being executed.
TRAC Actuator

TRAC Accumulator

Brake fluid leakage

ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±130±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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NGOK
OKNG
INSPECTION PROCEDURES
1Check voltage between terminals PR and E21 of ABS & TRAC ECU connector.
C
OK
P1. Remove ABS & TRAC ECU with connectors stillconnected.
2. Operate the engine for about 30 seconds at idle speed to raise the pressure of the TRAC actuator
to a high level.
1. Stop the engine and then turn ignition switch ON.
2. Measure voltage between terminals PR and E2 of ABS & TRAC ECU connector.
Voltage: 4 ± 8 V for more than 24 sec.
Check and replace ABS & TRAC ECU.
2Check for brake fluid leakage.
See page BR±150.
Repair brake fluid leakage and add fluid.
Replace TRAC accumulator.
If TRAC accumulator is replaced and the problem is still occurring, repl\
ace TRAC actuator.
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±131
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WIRING DIAGRAM
DTC55Brake Fluid Level Warning Switch Circuit
CIRCUIT DESCRIPTION
The brake fluid level warning switch sends the appropriate signal to the EC\
U when the brake fluid level drops.
DTC No.DTC Detecting ConditionTrouble Area
55Voltage at ECU terminal LBL is 0Vcontinuously for 10
sec. or more.

Brake fluid level.

Brake fluid level warning switch.

Short in brake fluid level warning switchcircuit.

ECU
Fail safe function: If trouble occurs in this circuit, the ECU cuts off current to the TRAC solenoid relay
and prohibits TRAC control.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±132±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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