LEXUS SC400 1991 Service Repair Manual

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 D squib circuit.
C
OK
Measure resistance between D+ and D± on spiral cable
side of connector between spiral cable and steering
wheel pad.
Resistance: 1 k
or higher
Go to step
.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±87
WhereEverybodyKnowsYourName

OKNG
OKNG
3Check center airbag sensor assembly.
C
OK
Hint
P1. Using a service wire, connect D+ and D±.
2. Using a service wire, connect P
+ and P±.
3. Connect negative (±) terminal cable to battery.
4. Clear malfunction.
5. Turn ignition switch LOCK, and wait at least 20 sec- onds.
6. Disconnect service wire of D
+ and D±.
7. Turn ignition switch ACC or ON, and wait at least 20
seconds.
1. Turn ignition switch LOCK, and wait at least 20 sec- onds.
2. Turn ignition switch ACC or ON, and wait at least 20 seconds.
3. Using SST, connect terminals Tc and E
1 of DLC2.
SST 09842±18020
4. Check diagnostic trouble code.
Diagnostic trouble code 13 is not output.
Codes other t han code 13 may be output at this time, but
this is not relevant to this check.
Replace center airbag sensor assembly.
4Check D squib.
C
OK
Hint
P1. Turn ignition switch LOCK.
2. Disconnect battery negative (±) terminal cable, and wait at least 90 seconds.
3. Connect steering wheel pad (squib) connector.
4. Connect negative (±) terminal cable to battery.
5. Clear malfunction.
1. Turn ignition switch LOCK, and wait at least 20 sec- onds.
2. Turn ignition switch ACC or ON, and wait at least 20 seconds.
3. Using SST, connect terminals Tc and E
1 of DLC2.
SST 09843±18020
4. Check diagnostic trouble code.
Diagnostic trouble code 13 is not output.
Codes other t han code 13 may be output at this time, but
this is not relevant to this check.
Replace steering wheel pad.
RS±88
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

OKNG
OKNG
From the results of the above inspection, the malfunctioning part can now be\
considered normal. To
make sure of this, use the simulation method to check.
5Check spiral cable.
C
OK
P1. Disconnect connector between center airbag sen-sor assembly and spiral cable.
2. Release airbag activation prevention mechanism on center airbag sensor assembly side of spiral
cable connector (See page RS±91).
Measure resistance between D
+ and D± on spiral cable
side of connector between spiral cable and steering
wheel pad.
Resistance: 1 M
or higher
Repair or replace spiral cable.
6Check harness between center airbag sensor assembly and spiral cable.
C
OK
P1. Disconnect center airbag sensor assembly con-
nector.
2. Release airbag activation prevention mechanism on center airbag sensor assembly connector (See
page RS±91 ).
Measure resistance between D
+ and D± on center air-
bag sensor assembly side of connector between center
airbag sensor assembly and spiral cable.
Resistance: 1 M
or higher.
Repair or replace harness or connector between center
airbag sensor assembly and spiral cable.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±89
WhereEverybodyKnowsYourName

OKNG
7Check center airbag sensor assembly.
C
OK
PConnect center airbag sensor assembly connector.
Measure resistance between D
+ and D± on center air-
bag sensor assembly side of connector between center
airbag sensor assembly and spiral cable.
Resistance: 1 k
or more
Replace center airbag sensor assembly.
From the results of the above inspection, the malfunctioning part can now be\
considered normal. To
make sure of this, use the simulation method to check.
RS±90±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

RELEASE METHOD OF AIRBAG ACTIVATION PREVENTION
MECHANISM
An airbag activation prevention mechanism is built into the connector for \
the squib circuit of the supplemen-
tal restraint system. When release of the airbag activation prevention mech\
anism is directed in the trouble-
shooting procedure, as shown in the illustration of the connectors 1 and 2 below\
, insert paper which is the
same thickness as the male terminal, between the terminal and the short spri\
ng.
CAUTION:
NEVER RELEASE the airbag activation prevention mechanism on the steering whee\
l pad connector.
NOTICE:
 Do not release the airbag activation prevention mechanism unless specifically directed by the
troubleshooting procedure.
 If the paper inserted is too thick the terminal and short spring may be \
damaged, so always use paper the
same thickness as the male terminal.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±91
WhereEverybodyKnowsYourName

DTC14Open in D Squib Circuit
CIRCUIT DESCRIPTION
The squib circuit consists of the center airbag sensor assembly, spiral cable and the steering wheel pad (squib).
It causes the SRS to deploy when the SRS deployment conditions are satisfi\
ed.
For details of the function of each component, see FUNCTION OF COMPONENTS o\
n page RS±9. Diagnostic
trouble code 14 is recorded when an open is detected in the squib circuit.
DTC No.Diagnosis
14
 Open circuit in D+ wire harness or D± wire harness of squib.
 Squib malfunction.
 Spiral cable malfunction.
 Center airbag sensor assembly malfunction.
RS±92±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

WIRING DIAGRAM
DIAGNOSTIC CHARTDIAGNOSTIC CHART
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±93
WhereEverybodyKnowsYourName

NGOK
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 D squib circuit.
C
OK
PDisconnect center airbag sensor assembly connector.
Measure resistance between D+ and D± on spiral cable
side of connector between spiral cable and steering
wheel pad.
Resistance: Below 1

Go to Step
.
RS±94
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

OKNG
OKNG
3Check spiral cable.
C
OK
PDisconnect connector between center airbag sensor
assembly and spiral cable.
Measure resistance between D
+ and D± on spiral cable
side of connector between spiral cable and steering
wheel pad.
Resistance: Below 1

Repair or replace spiral cable.
4Check harness between center airbag sensor assembly and spiral cable.
C
OK
Measure resistance between D+ and D± on center air-
bag sensor assembly side of connector between center
airbag sensor assembly and spiral cable.
Resistance: Below 1

Repair or replace harness or connector between center
airbag sensor assembly and spiral cable.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±95
WhereEverybodyKnowsYourName

OKNG
OKNG
5Check center airbag sensor assembly.
C
OK
Hint
P1. Connect connector to center airbag sensor connec-
tor.
2. Connect connector between center airbag sensor assembly and spiral cable.
3. Using a service, wire, connect D
+ and D±. P+ and
P±.
4. Connect negative (±) terminal cable to battery and wait at least 2 second.
1. turn ignition switch ACC or ON, and wait at least 20
seconds.
Clear malfunction code. Turn ignition switch LOCK
and wait at least 20 seconds.
2. Turn ignition switch ACC or ON, and wait at least 20
seconds.
3. Using SST, connect terminals Tc and E
1 of DLC2.
SST 09843±18020
4. Check diagnostic trouble code.
Diagnostic trouble code 14 is not output.
Codes other than code 14 may be output at this time ,
but this is not relevant to this check.
Replace center airbag sensor assembly.
6Check D squib.
C
OK
Hint
P1. Turn ignition switch LOCK.
2. Disconnect battery negative (±) terminal cable, and wait at least 90 seconds.
3. Connect steering wheel pad (squib) connector.
4. Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
1. Turn ignition switch ACC or ON, and wait at least 20
seconds.
Clear malfunction code. Turn ignition switch LOCK
and wait at least 20 seconds.
2. Turn ignition switch ACC or ON, and wait at least 20
seconds.
3. Using SST, connect terminals Tc and E
1 of DLC2.
SST 09843±18020
4. Check diagnostic trouble code.
Diagnostic trouble code 14 is not output.
Codes other t han code 14 may be output at this time, but
this is not relevant to this check.
Replace steering wheel pad.
From the results of the above inspection, the malfunctioning part can now be\
considered normal. To
make sure of this, use the simulation method to check.
RS±96±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName