1991 LEXUS SC300 battery

Check center airbag sensor assembly.
Diagnostic code 14 is not output.(1) Connect connector to center airbag sensor
connector.
(2) Connect connector between center airbag sensor assembly and spiral cable.
(3) Using a service wire, connect D+ and D± on spiral cable side of connector between spiral
cable and steering wheel pad.
(4) Connect negative (±) terminal cable to battery,
and wait at least 2 seconds.
Check squib.
(1) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(2) Using SST, connect terminals Tc and E1 of TDCL.
SST 09843±18020
(3) Check diagnostic code.
(1) Turn ignition switch LOCK.
(2) Disconnect battery negative (±) terminal cable, and wait at least 20 seconds.
(3) Connect steering wheel pad (squib) connector.
(4) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
Diagnostic code 14 is not output. (1) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(2) UsingSST, connect terminals Tc and E1 of TDCL.
SST 09843±18020
(3) Check diagnostic code. Codes other than code 14 may be output at this
time, but this is not relevant to this check
Codes other than 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 no\
w be considered normal.
To make sure this, use the simulation method to check. Replace center airbag sensor assembly.
AB±66±
SRS AIRBAG Troubleshooting
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INSPECTION PROCEDURE
When storing steering wheel pad, keep upper
surface of pad facing upward.
Preparation.
(1) Disconnect battery negative (±) terminal cable, and wait at least 20 seconds.
(2) Remove steering wheel pad (See page AB±14).
Disconnect center airbag sensor assembly connector.
Check front airbag sensor circuit (Measure resistance between terminals +SR
and ±SL and ±SL of center airbag sensor assembly connector.).
Measure resistance between terminals +SR and ±SR,
+SL and ±SL of harness side connector of center air-
bag sensor assembly.
Resistance: 755
± 885

Go to step
AB±70±
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3
Codes other than code 15 may be output at this
time, but this is not relevant to this check.Replace front airbag sensor.
NG
OK
(1) Turn ignition switch ACC or ON, and wait at least 20
seconds.
(2) Using SST, connect terminals Tc and E
1 of TDCL.
SST 09843±18020
(3) Check diagnostic code.
Check center airbag sensor assmbly.
Check front airbag sensor.
Replace center airbag sensor assembly.NG
OK
Diagnostic code 15 is not output.
(1) Connect connector to center airbag sensor
assembly.
(2) Using a service wire, connect D+ and D± on spiral cable side of connector between spiral
cable and steering wheel pad.
(3) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
From the results of the above inspection, the malfunctioning part can no\
w be considered normal.
To make sure of this, use the simulation method to check.
4
Disconnect front airbag sensor connector. Measure resistance between each terminal of
front airbag sensor.

Do not touch ohmmeter probes strongly
against terminals of front airbag sensor.

Make sure the front airbag sensor connector
is properly connected.
Terminal Resistance
Below 1 
755
 ±885 
1 M or higher
+S ± +A
+S ± ±S
±S ± ±A
±
SRS AIRBAG TroubleshootingAB±71
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Check ECU±B fuse.
NG
OK
1
6Go to step
(1) Disconnect battery negative (±) terminal cable, and wait at least 20 seconds.
(2) Remove steering wheel pad (See page AB±14).
When storing steering wheel pad, keep upper
surface of pad facing upward.
NG
OKRepair.
Check connection of center airbag sensor assembly connector.2
3Preparation.
INSPECTION PROCEDURE
HINT: If airbag warning light does not light up, perform the following troubl\
eshooting:
±
SRS AIRBAG TroubleshootingAB±77
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4
5
6
Check terminal LA of center airbag sensor assem-
bly and electrical connection check mechanism.
If normal, replace center airbag sensor assembly.
NG
OK
(1) Disconnect negative (±) terminal cable from battery.
(2) Connect center airbag sensor assembly.
(3) Connect negative (±) terminal cable to battery.
(4) Turn ignition switch ACC or ON. Voltage: 10±14 V
Check operation of airbag warning light.
(1) Disconnect center airbag sensor assembly.
(2) Connect negative (±) terminal cable to battery.
(3) Turn ignition switch ACC or ON.
Measure voltage LA terminal of harness side
connector of center airbag sensor assembly.
Repair airbag warning light circuit
(see page BE±150).
NG
Using simulation method, reproduce
malfunction symptoms (See page In±20).NG
OK
Check airbag warning light circuit.
Does airbag warning light come on?
Is new ECU±B fuse burnt out again?
From the results of the above inspection, the malfunctioning part can now be considered norm\
al. To
make sure of this, use the simulation method to check.
Check harness between ECU±B fuse and airbag warning light, and ECU±B fus\
e and center airbag sensor
assembly.
AB±78±
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OK
Check operation of airbag warning light.
NG1
WIRING DIAGRAM
2Is diagnostic code 41 output again? System is normal.
Check harness between ECU±B
fuse and center airbag sensor as-
sembly. If normal, replace center
airbag sensor assembly.
Perform troubleshooting according to
malfunction code output. NO
YES
Diag. Code 41Malfunction Stored in Memory
CIRCUIT DESCRIPTION
If a malfunction occurs in the airbag system, malfunction codes 11 to 31 may be output, and when the
battery is disconnected after the malfunction is repaired, malfunction codes 11 to 31 will be cleared,
but code 41 will be output instead.
So long as the cancellation operation for a malfunction stored in memory (\
See page
AB±32) is not per-
formed, code 41 is stored in the center airbag sensor assembly and the airbag w\
arning light remains
lit up.
Code No.Diagnosis
41
Malfunction recorded in memory.41
Center airbag sensor assembly malfunction.
DIAGNOSTIC CHART
AB±82±
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1
(1) Turn ignition switch LOCK.
(2) Disconnect negative (±) terminal cable frombattery.
(3) Disconnect center airbag sensor assembly connector.
(4) Connect negative (±) terminal cable to battery.
Does airbag warning light turn off?
Check airbag warning light circuit or terminal
AB circuit of TDCL or check connector.NG
YES
Check operation of airbag warning light.
Replace center airbag sensor assembly.
INSPECTION PROCEDURE
±
SRS AIRBAG TroubleshootingAB±85
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NGOK
Check center airbag sensor assembly.3
(1) Disconnect negative (±) terminal cable from
battery, and wait at least 20 seconds.
(2) Turn ignition switch lock.
(3) Disconnect center airbag sensor assembly
connector.
(4) Using a service wire, connector terminal Tc of center airbag sensor assembly connector to
body ground.
(5) Install the center airbag sensor assembly.
(6) Connect negative (±) terminal cable to battery.
(7) Turn ignition switch ACC or ON.
Check operation of airbag warning light.
Airbag light comes on.
Check harness between center airbag sensor
assembly and TDCL or check connector.
Replace center airbag sensor assembly.
C
P
OK
CautionNever turn ignition switch ACC or ON and
never connect negative (±) terminal to battery
before the center airbag sensor assembly is
installed.
±
SRS AIRBAG TroubleshootingAB±89
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