1991 LEXUS SC400 wiring

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)
WhereEverybodyKnowsYourName

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)
WhereEverybodyKnowsYourName

WIRING DIAGRAM
DIAGNOSTIC CHARTDIAGNOSTIC CHART
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±135
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WIRING DIAGRAM
DTC61TRAC ECU Communication Circuit Malfunc-
tion.
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
61
Either of the following (1) or (2) continues for more than
8 sec.:
(1) Vehicle speed signal of 4 wheels is less than 1 km/h
(1 mph) when TRCO signal is input.
(2) THFA signal is 0V when TRCO signal is not input.

Open or short in THFA, TRCO circuit

ABS & TRAC ECU

TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±138±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
WhereEverybodyKnowsYourName

BE±78).
BR±74 ).
IN±33 ).
WIRING DIAGRAM
Stop Light Switch Circuit
CIRCUIT DESCRIPTION
The stop light switch senses whether the brake pedal is depressed or releas\
ed, and sends a signal to the ECU.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±142±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
WhereEverybodyKnowsYourName

WIRING DIAGRAM
ABS Warning Light Circuit
CIRCUIT DESCRIPTION
If the ECU detects trouble, it lights the ABS warning light while at the s\
ame time prohibiting ABS control.
At this time, the ECU records a diagnostic trouble code in memory.After removing the short pin of the DLC1,
connect a DLC1 or connect terminals Tc and E1 of the DLC2 to make the ABS warning light to blink and
output the diagnostic trouble code.DIAGNOSTIC CHARTPerform troubleshooting in accordance with the
chart below for each trouble symptom.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Perform troubleshooting in accordance with the chart below for each trouble sym\
ptom.
 


ABS warning light does not light up 


Go to step
 

ABS warning light remains on 

Go to step
BR±144±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
WhereEverybodyKnowsYourName

IN±33).
WIRING DIAGRAM
Tc Terminal Circuit
CIRCUIT DESCRIPTION
Connecting between terminals Tc and E1 of the DLC1 or the DLC2 causes the ECU to display the diagnos-
tic trouble code by flashing the ABS warning light.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±148±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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IN±33 ).
WIRING DIAGRAM
Ts Terminal Circuit
CIRCUIT DESCRIPTION
The sensor check circuit detects abnormalities in the speed sensor signal w\
hich can not be detected with
the diagnostic trouble code check.Connecting terminals Ts and E1 of the DLC1 in the engine compartment
starts the check.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±150±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
WhereEverybodyKnowsYourName