1991 LEXUS SC400 sensor

Preperation.
Check squib circuit.
Check spiral cable.Check harness between center airbag
sensor assembly and spiral cable.
Check center airbag sensor assembly.
Check squib.
From the results of the above inspection, the
malfunctioning part can now be considered
normal. To make sure of this, use the simula-
tion method to check. Go to step
Repair or replace spiral cable.
Repair or replace harness or con-
nector between center airbag sen-
sor assembly and spiral cable. Replace center airbag
sensor assembly
Replace steering wheel pad.
WIRING DIAGRAM
DIAGNOSTIC CHARTDIAGNOSTIC CHART
±
SRS AIRBAG TroubleshootingAB±63
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INSPECTION PROCEDURE
(1) Disconnect battery negative (±) terminal cable, and wait at least 20 seconds.
(2) Remove steering wheel pad (See page AB±14).
Measure resistance between D+ and D± on spiral
cable side of connector between spiral cable and
steering wheel pad.
Preparation.
Resistance: Below 1

When storing steering wheel pad, keep upper sur-
face fo the pad facing upward.
Disconnect center airbag sensor assembly connec-
tor.
Check squib circuit.
Go to step
AB±64±
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Check spiral cable.
Repair or replace spiral cable.
Measure resistance between D+ and D± on center
airbag sensor assembly side of connector between
center airbag sensor assembly and spiral cable.
Check harness between center airbag sensor assembly and spiral
cable.
Resistance: Below 1

Measure resistance between D+ and D± on spiral
cable side of connector betweenspiral cable and
steering wheel pad.
Resistance: Below 1


Disconnect connector between center airbag sensor
assembly and spiral cable.
Repair or replace harness or connector
between center airbag sensor assembly
and spiral cable.
±
SRS AIRBAG TroubleshootingAB±65
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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±
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Diag. Code 15\
 \
Open in Front Airbag Sensor Circuit
CIRCUIT DESCRIPTION
The front airbag sensor detects the deceleration force in a frontal collisi\
on and is located in the front fender
on the left and right sides.
For details of the function of each component, see FUNCTION OF COMPONENT\
S on page AB±5.
Diagnostic code 15 is recorded when an open is detected in the front air\
bag sensor circuit.
NOTICE: The front airbag sensor connector is equipped with an electrical connection \
check mechanism
for the purpose of detecting an open in the front airbag sensor (See page AB±7). This mechanism is
constructed so that when the terminals of the front airbag sensor have been connect\
ed (when the connec-
tor housing lock is in the locked condition), the connection detection \
pin on the wire harness side connects
with the terminals for diagnosis use on the sensor side. If the connector is\
not properly connected, the diag-
nosis system may detect only a malfunction code, even though the airbag syste\
m is functioning normally.
When connecting the front airbag sensor connector, make sure it is connected properly. If diagnostic code
15 is displayed after the front airbag sensor connector has been connect\
ed, check again that it is properly
connected.
 

Code No.
\
 
\

\
Diagnosis
 




15
\
 
\


\

\



Open circuit in +S wire harness or ±S wire harness of front airbag s\
ensor.

Front airbag sensor malfunction.

Malfunction of electrical connection check mechanism of front airbag se\
nsor.

Center airbag sensor assembly malfunction.
AB±68±
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Preperation.
Check front airbag sensor circuit.
(Measure resistance between terminals +SR
and ±SR, +SL and ±SL of center airbag sen-
sor assembly connector.)
Check center airbag sensor assembly.From the results of the above inspection, the
malfunctioning part can now be considered nor-
mal. To make sure of this, use the simulation
method to check.
Check front airbag sensor.
Check harness between center airbag
sensor assembly and front airbag sensor.
Replace front airbag sensor connector
(See page AB±20). Replace center airbag sensor
assembly. Go to step
Replace front airbag sensor.
Repair or replace harness or con-
nector between center airbag sen-
sor assembly and front airbag sen-
sor (See page AB±20).
WIRING DIAGRAM
DIAGNOSTIC CHARTDIAGNOSTIC CHART
±
SRS AIRBAG TroubleshootingAB±69
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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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