1991 LEXUS SC400 wiring

IN±33).
WIRING DIAGRAM
DTC41IG Power Source Circuit
CIRCUIT DESCRIPTION
This is the power source for the ECU and becomes power source for the CPU an\
d actuators.
DTC No.DTC Detecting ConditionTrouble Area
41
When either of the following (1) or (2) is detected:
(1) Voltage at ECU terminal IG is less than 9.5 V for more than 10 sec. while engine speed is 500 rpm
or higher.
(2) Voltage at ECU terminal IG is more than 17 V for more than 5 sec.

Battery

IC regulator

Open or short in power source circuit

ECU
Fail safe function: If trouble occurs in the power source circuit, the E\
CU prohibits TRAC control.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±192±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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OKNG
4Check ECU±IG fuse.
C
OK
PRemove ECU±IG fuse from J/B No. 1.
Check continuity of ECU±IG fuse.
Continuity
Check for short in all the harness and components con-
nected to ECU±IG fuse (See attached wiring diagram).
Check for open in harness and connector between
TRAC ECU and battery (See page IN±33).
BR±194±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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WIRING DIAGRAM
DTC43ABS & TRAC ECU Malfunction
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
43ABS control system or TRAC (BRAKE) control system
or communication circuit is abnormal.
ABS & TRAC ECU

Open or short in BRFA circuit
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±196±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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WIRING DIAGRAM
DTC44NE Signal Circuit
CIRCUIT DESCRIPTION
The TRAC ECU receives engine speed signals (NE signals) from the ECM.
DTC No.DTC Detecting ConditionTrouble Area
44No signal is input to terminal NEO 0.24 sec. after trac-
tion control is initiated.
Open or short in NEO circuit

ECM

TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±198±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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WIRING DIAGRAM
BR±202±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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WIRING DIAGRAM
BR±210±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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IN±29).
WIRING DIAGRAM
DTC49Engine Communication Circuit
CIRCUIT DESCRIPTION
This circuit is used to send ignition timing retard request signals from the TRAC ECU to\
the ECM in order to retard
the engine ignition timing.
DTC No.DTC Detecting ConditionTrouble Area
49TR2 output voltage differs from TR2 monitorvoltage in
TRAC ECU.
Open or short in TR2 circuit

ECM

TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±216±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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TR±11
WIRING DIAGRAM
DTC51Engine Malfunction Detection Circuit
CIRCUIT DESCRIPTION
If trouble (trouble which causes the malfunction indicator light to light\
up) occurs in the engine control system,
this circuit senses the trouble and prohibits TRAC control.
DTC No.DTC Detecting ConditionTrouble Area
51
Either of the following (1) and (2) continues formore
than 1 sec.:
(1) Engine speed: 500 RPM or more
(2) Voltage of TRAC ECU terminal TR5: 1 V or less
Short in TR5 circuit

ECM

TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±218±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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