check engine LEXUS SC400 1991 Service Repair Manual

1. DISCONNECT NEGATIVE (±) TERMINAL CABLE FROMBATTERY
CAUTION: Work must be started after 90 seconds from
the time the ignition switch is turned to the ªLOCKº posi-
tion and the negative (±) terminal cable is disconnected
from the battery.
(See page RS±2)
2. REMOVE ENGINE UNDER COVER
(See page BO±12)
3. REMOVE FRONT AIRBAG SENSOR
(a) Disconnect the connector.
(b) Remove the bolt, the nut and the sensor.
4. INSTALL FRONT AIRBAG SENSOR
(a) Install the sensor with the arrow on the sensor facing toward the front of the vehicle.
Torque: 25 N Vm (260 kgf Vcm, 19 ft Vlbf)
NOTICE:
w Make sure the sensor is installed to the specified torque.
w If the sensor has been dropped, or there are cracks, dents
or other defects in the case, brackets or c onnector,
replace the sensor is removed, always replace the set bolt
and the nut with new one.
w The sensor set bolt and the nut have been anti±rust
treated. When the sensor is removed, always replace the
set bolt and the nut with new ones.
w After installation, shake the sensor to check that there is
no looseness.
w The front sensor is equipped with an electrical
connection check mechanism. Be sure to lock this
mechanism securely when connecting the connector. If
the connector is not securely locked, a malfunction code
will be detected by the diagnosis system.
w Check that the dimensions of the body where the front
airbag sensor is installed match those in the body
dimension drawings in the BODY section.
(The SRS may malfunction, or may not work, if the
dimensions of the sensor mount is not correct.)
5. INSTALL ENGINE UNDER COVER
6. CONNECT NEGATIVE (±) TERMINAL CABLE TO BATTERY
±
SUPPLEMENTAL RESTRAINT SYSTEM FRONT AIRBAG SENSORRS±43
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YESNO
INSPECTION PROCEDURE
1Preparation.
P1. Turn ignition switch LOCK.
2. Disconnect battery negative (±) terminal cable, andwait at least 90 seconds.
3. Connect battery negative (±) terminal cable.
4. Disconnect center airbag sensor assembly con- nector.
5. Turn ignition switch ON. But do not start engine.
6. Measure voltage at IG
2 or ACC on connector wire
harness side of center airbag sensor assembly and
operate electric system (defogger, wiper, headlight,
heater blower, etc.)
Voltage: 6 V ± 11.5 V at IG
2 and ACC.
7. Turn electric system switch OFF.
8. Turn ignition switch LOCK.
9. Disconnect battery negative (±) terminal cable, and wait at least 90 seconds.
10. Remove voltmeter and connect center airbag sen- sor assembly connector.
11. Connect battery negative (±) terminal cable.
2Does SRS warning light turn off after approx. 10 seconds?
C
PTurn ignition switch ACC or ON and wait at least 20 sec-
onds.
Clear malfunction code. Turn ignition switch LOCK and
wait at least 20 seconds.
Operate electric system checked in
(5) and check
that SRS warning light goes off after approx. 10 sec-
onds.
Check diagnostic trouble code, and if a malfunction code
is output, perform trouble shooting according to mal-
function code. If a normal code is output, replace center
airbag sensor assembly.
Check battery and charging system.
(See page CH±1)
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±69
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3. INSTALL BRAKE CALIPERInstall the brake caliper to the steering cnuckle with the 2
bolts.
Torque: 118 N Vm (1,200 kgf Vcm, 87 ft Vlbf)
4. STABILIZE SUSPENSION
(a) Install the front wheel and jack down the vehicle.
Torque: 103 N Vm (1,050 kgf Vcm, 76 ft Vlbf)
(b) Bounce the vehicle up and down several times to stabilize the
suspension.
5. TORQUE ADJUSTING CAMS AND NUTS
(a) Jack up the vehicle and remove the front wheel.
(b) Support the lower arm with jack.
(c) Align the matchmarks and torque the adjusting cams and nuts with the vehicle weight on the suspension.
Torque: 226 N Vm (2,300 kgf Vcm, 166 ft Vlbf)
6. INSTALL ENGINE UNDER COVER
7. INSTALL FRONT WHEEL
Torque: 103 N Vm (1,050 kgf Vcm, 76 ft Vlbf)
8. CHECK FRONT WHEEL ALIGNMENT
(See page SA±5)
SA±44
±
SUSPENSION AND AXLE FRONT SUSPENSION
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DIAGNOSTIC CHART
DIAGNOSTIC
CHART
Check for short in all the harness and
components connected to IGN fuse.
Check voltage of terminal M±REL.
Check for open in harness and connector
between battery and ECU.
Check and replace ECU.
Replace ignition switch.
Repair or replace harness or
connector.
Repair or replace harness or
connector.
Check for open and short in harness and
connector between terminal M REL and body
ground.
Replace EFT main relay.
Check voltage of terminal IGSW.
Check IGN fuse.
Check continuity between terminals E1 and
body ground.
Check voltage of ECU power source.
Proceed to next circuit inspection
shown on matrix chart (See page
TR±35
).
Check ignition switch.
Check EFT fuse.
Check EFT main relay.
Check and repair or harness or connector
between EFI fuse and battery.
Check for short in all the harness and
components connected to EFI fuse.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±125
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NGOK
OKNG
NGOK
INSPECTION PROCEDURE
1Check voltage between terminals + B, + B1 and E1 of engine & ECT ECU connecto\
r.
C
OK
P(2) Connect the Check Harness A.(See page TR±30)
(2) Turn ignition switch on.
Measure voltage between terminals + B, + B1 and E1
of engine & ECT ECU connector.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on matrix chart
2Check for open in harness and connector between terminals E1 of engine &\
ECT ECU and body
ground (See page IN±27).
Repair or replace harness or connector.
3Check voltage between terminal IG SW of engine & ECT ECU connector and b\
ody ground.
C
OK
PTurn ignition switch on.
Measure voltage between terminal IG SW of engine &
ECT ECU connector and body ground.
Voltage: 10 ± 14 V
Go to step 6.
TR±126
±
ENGINE TROUBLESHOOTING Circuit Inspection
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OKNG
OKNG
4Check IGN Fuse.
C
OK
PRemove IGN fuse from J/B No.1.
Check continuity of IGN fuse.
Continuity.
Check for short in all the harness and components con-
nected to IGN fuse (See attached wiring diagram).
5Check ignition switch.
C
OK
PRemove under cover and finish panel.
Check continuity between terminals.
continuity
Replace ignition switch.
Check and repair harness and connector between
battery and ignition switch, ignition switch and en-
gine & ECT ECU.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±127
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OKNG
OKNG
6Check voltage between terminal M±REL of engine & ECT ECU connector and bod\
y ground.
C
OK
PTurn ignition switch on.
Measure voltage between terminal M±REL of engine &
ECT ECU connection and body ground.
Voltage: 10 ± 14 V
Check and replace engine & ECT ECU.
7Check EFI
C
OK
PRemove EFI fuse R/B No.2.
Check continuity of EFI fuse.
Continuity
Rep
TR±128
±
ENGINE TROUBLESHOOTING Circuit Inspection
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OKNG
OKNG
8Check EFI main relay.
C
OK
P
C
OK
Remove EFI main relay.
Check continuity between terminals of EFI main relay
shown below.
(2) Apply battery voltage between terminals 1 and 3.
(2) Check continuity between terminals 2 and 4.
Replace EFI main relay.
9Check for open and short in harness and connector between terminal M±REL o\
f engine & ECT
ECU and body ground (See page IN±27).
Repair or replace harness or connector.
Check and repair harness or connector between
EFI fuse and battery.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±129
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Check EFI fuse.
Check voltage of terminal BATT.
Check operation for the back±up.
Proceed to next circuit inspection
shown on matrix chart (See page TR±39).
Check for short in all the harness and
components connected to EFI fuse.
Check and repair harness or connector
between battery, EFI fuse and ECU.
Check and replace fuse.
WIRING DIAGRAM
Back Up Power Source Circuit
CIRCUIT DESCRIPTION
Battery voltage is supplied to terminal BATT of the ECU even when the ignition switch is off for use
by the diagnostic code memory and air±fuel ratio adaptive control val\
ue memory, etc.
DIAGNOSTIC CHART
TR±126±
ENGINE TROUBLESHOOTING Circuit Inspection
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OKNG
OKNG
YESNO
INSPECTION PROCEDURE
1Check EFI fuse.
C
OK
PRemove EFI fuse from R/B No. 2
Check continuity of EFI fuse.
Continuity
Check for short in all the harness and components
connected to EFI fuse (See attached wiring diagram).
2Check voltage between terminal BATT of engine (& ECT) ECU connector and body ground.
C
OK
PConnect the Check Harness A. (See page TR±34)
Measure voltage between terminal BATT of engine
(& ECT) ECU connector and body ground.
Voltage: 10 ± 14 V
Check and repair harness or connector between engine
(& ECT) ECU and EFI fuse, EFI fuse and battery.
3Are the diagnostic trouble codes still in the memory when the ignition s\
witch is turned OFF?
Check and replace engine (& ECT) ECU.
Proceed to next circuit inspection shown on
matrix chart (See page TR±39).
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±127
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