steering LEXUS SC400 1991 Service Repair Manual

SR±52).
IN±33).
WIRING DIAGRAM
CIRCUIT INSPECTION
ECU Power Source Circuit
CIRCUIT DESCRIPTION
The ECU power source also supplies power to the CPU and sensor, etc. Power is supplied to the ECU even
when the ignition switch is off.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
SR±62±
STEERING STEERING COLUMN
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NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals ECU±B and ECU±E of ECU connector.
C
OK
PRemove ECU with connectors still connected.
Measure voltage between terminals ECU±B and ECU±
E of ECU connector.
Voltage: 10 ~ 14 V
Proceed to next circuit inspection shown on matrix chart
(See page SR±52).
2Check continuity between terminal ECU±E of ECU connector and body gro\
und.
C
OK
Measure resistance between terminal ECU±E of ECU
connector and body ground.
Resistance: 1
or less
Repair or replace harness or connector.
Go to Step
.
±
STEERING STEERING COLUMNSR±63
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OKNG
3Check DOME Fuse.
C
OK
PRemove DOME Fuse from R/B No. 2.
Check continuity of DOME Fuse.
Continuity
Check for short in all the harness and components con-
nected to DOME Fuse (See attached wiring diagram).
Check harness and connector between ECU and
battery (See page
IN±33).
SR±64±
STEERING STEERING COLUMN
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±MEMO±
±
STEERING STEERING COLUMNSR±65
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OKNG
INSPECTION PROCEDURE
1Preparation.
P1. Disconnect battery negative (±) terminal cable, andwait at least 90 seconds.
2. Remove steering wheel pad (See page RS±19).
3. Disconnect connectors of front passenger airbag assembly (See page RS±32).
Caution: Store the steering wheel pad with the
surface facing upward.
2Check P squib circuit.
C
OK
Measure resistance between P+ and P± on center air-
bag sensor assembly side of connector between center
airbag sensor assembly and front passenger airbag as-
sembly.
Resistance: 1 k
or higher
Go to step
.
RS±112
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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OKNG
1Preparation.
P1. Disconnect battery negative (±) terminal cable, andwait at least 90 seconds.
2. Remove steering wheel pad (See page RS±19).
3. Disconnect connectors of front passenger airbag assembly (See page RS±32).
Caution: Store the steering wheel pad with the
surface facing upward.
2Check P squib circuit.
C
OK
PDisconnect center airbag sensor assembly connector.
Measure resistance between P
+ and P± on center air-
bag sensor assembly side of connector between center
airbag sensor assembly and front passenger airbag as-
sembly.
Resistance: Below 1

Repair or replace harness or connector between center
airbag sensor assembly and front passenger airbag as-
sembly.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±117
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YESNO
INSPECTION PROCEDURE
1Does SRS warning light turn off?
C
Hint
P1. Turn ignition switch LOCK.
2. Disconnect negative (±) terminal cable from battery
and wait at least 90 seconds.
3. Remove steering wheel pad (See page RS±19).
4. Disconnect connectors of front passenger airbag assembly (See page RS±32).
5. Disconnect center airbag sensor assembly con- nector.
6. Connect negative (±) terminal cable to battery.
Check operation of SRS warning light.
Ignition Switch is LOCK position.
Check SRS warning light circuit or terminal AB circuit of
DCL1 or DLC2.
Replace center airbag sensor assembly.
RS±120±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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NGOK
3Check center airbag sensor assembly.
C
OK
P1. Turn ignition switch LOCK.
2. Disconnect battery negative (±) terminal cable, andwait at least 90 seconds.
3. Remove steering wheel pad (See page RS±19).
4. Disconnect connectors of front passenger airbag assembly (See page RS±32).
Check operation of SRS warning light.
SRS warning light comes on.
Check harness between center airbag sensor assembly
and DLC1 or DLC2.
Replace center airbag sensor assembly.
RS±124±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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NGOK
HINT: If the diagnostic trouble code is continuously displayed, perform the f\
ollowing troubleshooting.
1Check resistance between terminal Tc of center airbag sensor assembly and body ground.
C
OK
P1. Turn ignition switch LOCK.
2. Disconnect center airbag sensor assembly con-nector.
3. Disconnect battery negative (±) terminal cable, and wait at least 90 seconds.
4. Remove steering wheel pad (See page RS±19).
5. Disconnect connectors of front passenger airbag assembly (See page RS±32).
Check resistance between terminal Tc of center airbag
sensor assembly and body ground.
Resistance: 1 M
or higher
Replace center airbag sensor assembly.
Repair or replace harness or connector.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±125
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SERVICE SPECIFICATIONS
SERVICE DATA
RS02S±01
\
\
FRONT AIRBAG SENSOR\
 \

\
\

S ±
A\
 \
755±855

\
\

S ± S\
 \
1 M
or Higher
\
\
 S ± A\
 \
Less than 1

TORQUE SPECIFICATIONS
RS02T±07
\
\
Part tightened NVm kgf Vcm ft Vlbf
\
\
Steering wheel 35 360 26
\
\
Steering wheel pad 7.4 75 65 in. Vlbf
\
\
Front passenger airbag assembly 21 210 15
\
\
Front airbag sensor 25 260 19
\
\
Center airbag sensor assembly 15 150 11
RS±126±
SUPPLEMENTAL RESTRAINT SYSTEM SERVICE SPECIFICATIONS
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