ect LEXUS SC300 1991 Service Repair Manual

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 P circuit.
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 P
+ and P± on center air-
bag sensor assembly side of connector between airbag
sensor assembly and front passenger airbag assembly.
Resistance: 1 M
of higher
Repair or replace harness or connector between center
airbag sensor assembly and front passenger airbag as-
sembly.
6Check center airbag sensor assembly.
C
OK
PConnect 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: 1 k
or higher
Replace center airbag sensor assembly.
From the results of the above inspection, the malfunction part can now be con\
sidered normal. To make
sure of this, use the simulation method to check.
RS±114±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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DTC54Open in P Squib Circuit
CIRCUIT DESCRIPTION
The squib circuit consists of the center airbag sensor assembly and front p\
assenger airbag assembly. It causes
the SRS to deploy when the SRS deployment conditions are satisfied. For det\
ails of the function of each compo-
nent, see FUNCTION OF COMPONENTS on page RS±10.
Diagnostic trouble code 54 is recorded when an open is detected in the s\
quib circuit.
DTC No.Diagnosis
54

Open circuit in P+ wire harness and P± wire harness of squib.

Squib malfunction.

Center airbag sensor malfunction.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±115
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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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OKNG
OKNG
3Check 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 wiring harness connector.
3. Using a service wire, connect D
+ and D±, P+ and P±.
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 54 is not output.
Codes other t han code 54 may be output at this time, but
this is not relevant to this check.
Replace center airbag sensor assembly.
4Check P squib.
C
OK
Hint
P1. Turn ignition switch LOCK.
2. Disconnect battery negative (±) terminal cable, and
wait at least 90 seconds.
3. Connect front passenger airbag assembly connec- tor.
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 54 is not output.
Codes other t han code 54 may be output at this time, but
this is not relevant to this check.
Replace front passenger airbag 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±118±
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WIRING DIAGRAM
SRS Warning Light System (Always Lit Up, when ignition switch in
LOCK position)
CIRCUIT DESCRIPTION
The SRS warning light is located on the combination meter.
When the supplemental restraint system is normal, the SRS warning light ligh\
ts up for approx. 6 seconds after
the ignition switch is turned from LOCK position to ACC or ON position, and\
then turns off automatically.
If there is a malfunction in the supplemental restraint system, the SRS wa\
rning light lights up to inform the driver
of the abnormality.
When terminals Tc and E
1 of the DLC2 are connected, the diagnostic trouble code is displayed by \
the blinking
of the SRS warning light.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
HINT: If the SRS warning light is always lit up by a DTC check procedure, per\
form Tc T erminal circuit check proce-
dure (See page RS±121).
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±119
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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±
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Tc Terminal Circuit
CIRCUIT DESCRIPTION
By connecting terminal Tc and E1 of the DLC1 or DLC2, the center airbag sensor assembly is set in the di\
agnos-
tic trouble code output mode. The diagnostic trouble codes are displayed\
by the blinking of the SRS warning
light.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Troubleshooting for this system is different depending on whether the diagnostic trouble code is not displayed\
SRS warning light is always lit up with a DTC check procedure, or is displa\
yed without a DTC check procedure.
Confirm the problem symptoms first before selecting the appropriate troubleshoo\
ting procedure.
HINT: If the diagnostic trouble code is not displayed or SRS warning light is\
always lit up with a DTC check proce-
dure perform the following troubleshooting:
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±121
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NGOK
NGOK
INSPECTION PROCEDURE
HINT: If the diagnostic trouble code is not displayed, perform the following \
troubleshooting:
1Check voltage between terminals Tc and E1 of DLC1 or DLC2.
C
OK
PTurn ignition switch ACC or ON.
Measure voltage between terminals Tc and E
1 of DLC1
or DLC2.
Voltage: Battery positive voltage
Go to step
.
2Check voltage between terminal Tc of DLC1 or DLC2 and body ground.
C
OK
Measure voltage between terminal Tc of DLC1 or DLC2
and body ground.
Voltage: Battery positive voltage
Check harness between terminal E1 of DLC1 or DLC2
and body ground.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±123
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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±
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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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