ECU LEXUS SC400 1991 Service Repair Manual

NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminal TR2 of TRAC ECU and body ground.
C
OK
Hint
P1. Disconnect TRAC ECU connector.
2. Turn ignition switch on.
Measure voltage between terminal TR2 of TRAC ECU
and body ground.
Voltage: 8 ± 14 V
Check and replace TRAC ECU.
2Check for open and short in harness and connector between TRAC ECU and E\
CM (See page
IN±29).
Repair or replace harness or connector.
Check and replace ECM.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±217
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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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WIRING DIAGRAM
DTC61ABS & TRAC ECU Communication Circuit
Malfunction
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
61Malfunction in ABS & TRAC ECU communication cir-
cuit.
Open or short in ABSO, BRC, BRP circuit

ABS & TRAC ECU

TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±220±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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OKNG
NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals ABSO, BRC, BRP of TRAC ECU and body ground.
C
OK
Hint
PRemove TRAC ECU with connectors still connected.
Measure voltage between terminals ABSO, BRC, BRP
of TRAC ECU and body ground when ignition switch is
turned ON.
Voltage: ABSO, BRC: 6 ± 14 VBRP: About 7 V (Pulse)\
(Reference)
Check and replace TRAC ECU.
2Check voltage between terminals ABSO, BRC, BRP or TRAC ECU and body ground wi\
th TRAC
ECU connector is disconnected.
C
OK
Hint
PDisconnect TRAC ECU connector.
Measure voltage between terminals ABSO, BRC, BRP
or TRAC ECU connector and body ground when ignition
switch is turned ON.
Voltage: See step 1.
Check and replace TRAC ECU.
3Check for open and short in harness and connector between ABS & TRAC ECU and TRAC ECU
(See page IN±33).
Repair or replace harness or connector.
Check and replace ABS & TRAC ECU.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±221
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NOYES
OKNG
OKNG
OKNG
OKNG
INSPECTION PROCEDURES
1Is diagnostic trouble code output?
Perform diagnostic trouble code check on page BR±184.
Repair circuit indicated by the code output.
2Check TRAC cut switch
C
OK
P1. Remove TRAC cut switch.
2. Disconnect TRAC cut switch connector.
Measure re sistance between terminals 1 and 2 of TRAC
cut switch when TRAC cut switch is on and off.
Replace TRAC cut switch.
3Check for open and short in harness and connector between terminal CSW of TRA\
C ECU and
TRAC cut switch and body ground (See page IN±33
).
Repair or replace harness or connector.
4Check TRAC OF indicator light.
See combination meter troubleshooting on page BE±191.
Repair or replace combination meter.
5Check for open and short in harness and connector between terminal WT of TRAC ECU \
and bat-
tery or TRAC solenoid relay (See page IN±33
).
Repair or replace harness or connector.
Check and replace TRAC ECU.
BR±224±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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BR±160).
IN±33 ).
WIRING DIAGRAM
Tc Terminal Circuit
CIRCUIT DESCRIPTION
By connecting between terminals Tc and E1 of DLC1 or DLC2, the ECU displays the diagnostic trouble
code by blinking the TRAC indicator light.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±226±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals Tc and E1 of DLC 2 or DLC 1.
C
OK
PTurn ignition switch ON.
Measure voltage between terminals TC and E1 of DLC
2 or DLC 1.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on problem
symptoms chart (See page BR±160).
2Check for open and short in harness and connector between ABS & TRAC ECU, TRAC\
ECU and
DLC 2 (or DLC 1), DLC 2 (or DLC 1) and body ground (See page IN±33).
Repair or replace harness or connector.
Check and replace TRAC ECU.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±227
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2. INSTALL CALIPER
(a) Temporarily install the caliper on the torque plate with 2installation bolts.
(b) Hold the sliding pin and torque the installation bolt.
Torque: 34 N Vm (350 kgf Vcm, 25 ft Vlbf)
3. CONNECT FLEXIBLE HOSE
Install the flexible hose on the caliper with 2 new gaskets.
Torque: 30 N Vm (310 kgf Vcm, 22 ft Vlbf)
HINT: Insert the flexible hose lock securely in the lock hole in
the caliper.
4. FILL BRAKE R ESERVOIR WITH BRAKE FLUID AND
BLEED BRAKE SYSTEM
(See page BR±8)
5. CHECK FOR LEAKS
BR±36
±
BRAKE SYSTEM FRONT BRAKE (SC400)
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3. INSTALL PISTON SEAL AND PISTON IN CALIPER
4. INSTALL CYLINDER BOOT AND CYLINDER BOOT SETRING
CALIPER INSTALLATION
BR0ER±04
1. INSTALL FOLLOWING PARTS:
(a) 2 brake pads
(b) 2 anti±squeal springs
2. INSTALL CALIPER
(a) Temporarily install the caliper on the torque plate with 2installation bolts.
(b) Hold the sliding pin and torque the installation bolts.
Torque: 34 N Vm (350 kgf Vcm, 25 ft Vlbf)
3. CONNECT FLEXIBLE HOSE
Install the flexible hose on the caliper with 2 new gaskets.
Torque: 30 N Vm (310 kgf Vcm, 22 ft Vlbf)
HINT: Install the flexible hose lock securely in the lock hole
in the caliper.
4. FILL BRAKE R ESERVOIR WITH BRAKE FLUID AND
BLEED BRAKE SYSTEM
(See page BR±8)
5. CHECK FOR LEAKS
±
BRAKE SYSTEM REAR BRAKE (Disc Brake)BR±43
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BR0EX±01
ECU TERMINALS
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±57
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