1991 LEXUS SC400 traction control

BR±182±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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±MEMO±
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±183
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Location of Connectors in Body
SC300
BR±184±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±185
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WIRING DIAGRAM
IN±33).
DTC24TRAC Sub±Throttle Actuator Circuit
CIRCUIT DESCRIPTION
The sub±throttle actuator operates in accordance with signals from the E\
CU, controlling the opening and
closing of the sub±throttle valve.
DTC No.DTC Detecting ConditionTrouble Area
24Open or short in sub±throttle actuator circuit

TRAC fuse

Open or short in BM circuit.

Sub±throttle actuator.

Open or short in sub±throttle actuatorcircuit.

ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±186±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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OKNG
OKNG
INSPECTION PROCEDURES
1Check TRAC fuse.
C
OK
PRemove TRAC fuse from R/B No. 2.
Check continuity of TRAC fuse.
Continuity
Check for short in all harness and components con-
nected to TRAC fuse (See attached wiring diagram).
2Check voltage between terminals BM and GND or TRAC ECU.
C
OK
PRemove TRAC ECU with connectors still connected.
Measure voltage between terminals BM and GND of
TRAC ECU.
Voltage: 10 ± 14 V
Check and repair harness or connector.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±187
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OKNG
OKNG
3Check sub±throttle actuator.
C
OK
PDisconnect sub±throttle actuator connector.
Check continuity between each terminal of sub±throttle
actuator connector shown below.
Replace sub±throttle actuator.
4Check for open and short in harness and connector between TRAC ECU and sub±\
throttle actua-
tor (See page IN±33).
Repair or replace harness or connector.
Check and replace TRAC ECU.
BR±188±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
WhereEverybodyKnowsYourName

WIRING DIAGRAM
DTC25, 26, 27TRAC Sub±Throttle Valve
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
25
The difference between the sub±throttle sensor signal
voltage and the voltage required by the step count is 1
V or more.

Sub±throttle actuator.

Throttle body (sub±throttle valve is truck or operation is
faulty).

Sub±throttle position sensor.

Open or short in sub±throttle position sensor circuit.

ECM

TRAC ECU
26
Even when sub±throttle valve is driven to the fully open
position, input voltage at terminal VSH does not come
within range of the specifications 3 ~ 4.5 V.

Sub±throttle actuator.

Throttle body (sub±throttle valve is truck or operation is
faulty).

Sub±throttle position sensor.

Open or short in sub±throttle position sensor circuit.

ECM

TRAC ECU
27When input voltage at ECU terminal VSH is less than
the specification by about 2.5 V for 0.2 sec. or more.

Sub±throttle actuator (return spring is disconnected).

Sub±throttle position sensor.

Open or short in sub±throttle position sensor circuit.

ECM

TRAC ECU
C
OK
Hint
PRemove air cleaner and duct.
Open and close the sub±throttle valve manually and
check the condition during operation.
The valve should operate smoothly without catch-
ing.
If sub±throttle actuator, sub±throttle valve, sub±throttle
position sensor and harness are free from any defect,
ECM may be defective. If ECM is free from any defect,
TRAC ECU may be defective.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±189
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