ect LEXUS SC300 1991 Service Repair Manual

DIAGNOSTIC TROUBLE CODE
CLEARANCE
1. Using SST, connect terminals Tc and E1 of DLC2 or DLC1.SST 09843±18020
2. IG switch ON.
3. Clear the diagnostic trouble codes stored in ECU by depressing the brake pedal 8 or more times within 3 seconds.
4. Check that the TRAC indicator light shows the normal code.
5. Remove the SST from the terminals of DLC2 or DLC1.
HINT: Cancellation can also be done by removing the DOME
fuse, but in this case, other memory systems will also be can-
celled out.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±171
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DIAGNOSTIC TROUBLE CODE CHART
If a malfunction code is displayed during the diagnostic trouble code chec\
k, check the circuit listed for that code
in the table below and proceed to the page given.
HINT: If the TRAC indicator light lights up and the TRAC indicator light doe\
s not blink when the Diag. code is
checked, check the blinking pattern of the ABS warning light and perform trouble\
shooting of the ABS system.
BR±186BR±189
BR±190
BR±192
BR±196 BR±198
BR±200
BR±208
BR±216
BR±218
BR±220BR±189
BR±189
BR±190
BR±190
BR±190
BR±200 BR±208
*1: If a malfunction is detected, the TRAC OFF indicator light lights up.
*2: Indicator light does not lights up even if an error is detected.
*3: If a malfunction is detected, the TRAC OFF indicator light or TRAC i\
ndicator light light up.
BR±172
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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PROBLEM SYMPTOMS CHART
If a normal code is displayed during the diagnostic trouble code check but\
the problem still occurs, check
the circuits for each problem symptom in the order given in the table below\
and proceed to the page for
troubleshooting.
 Symptoms\
 \
Inspection Circuit See page
 


TRAC does not oper-
ate.\
 
\

\

Only when 1.~5. are all normal and the problem is still occurring, repla\
ce
the TRAC ECU. 

BR±170
 


\
 
\

\

1. Check the diagnostic trouble code, reconfirming that the normal code \
is
output. 


BR±192
 \
 \
2. IG Power Source Circuit. BR±228
 


\
 
\

\
3. Check the hydraulic circuit for leakage. 

BR±190
 \
 \
4. Speed Sensor Circuit. 
 \
 \
5. Park/neutral position switch circuit. 
 




TRAC indicator light
abnormal.\
 
\


\

\

1. TRAC Indicator Light Circuit.
2. TRAC ECU. 




BR±224
 


TRAC OFF indicator
light abnormal.\
 
\

\

Only when 1. and 2. are all normal and the problem is still occurring, r\
e-
place the TRAC ECU. 


BR±222
 \
 \
1. TRAC OFF indicator Light Circuit. 
 \
 \
2. TRAC cut switch circuit. 
 








Diagnostic trouble
code check cannot
be performed.\
 
\


\


\


\

\

Only when 1. and 2. are all normal and the problem is still occurring, r\
e-
place the TRAC ECU.
1. TRAC Indicator Light Circuit.
2. Tc terminal Circuit. 








BR±224
BR±226
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±173
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LOCATION OF CONNECTORS
Location of Connectors in Engine Compartment
SC300: BR±174
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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Location of Connectors in Instrument Panel
SC300:
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±177
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Location of Connectors in Instrument Panel
BR±180±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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Location of Connectors in Body
SC300
BR±184±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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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)
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