Lexus SC300 / Lexus SC400. Manual - part 795

OK

NG

OK

NG

5

Check P squib circuit.

OK

P

For the connector (on the center airbag sensor assem-
bly side) between the center airbag sensor assembly
and front passenger airbag assembly, measure the re-
sistance between P+, P– and body ground.

Resistance:

1 M

 or Higher

Repair or replace harness or connector between the cen-
ter airbag sensor assembly and front passenger airbag
assembly.

6

Check center airbag sensor assembly.

C

OK

Hint

P

1.

Connect connector to center airbag sensor assem-
bly.

2.

Using a service wire, connect D+ and D– on spiral
cable side of connector between spiral cable and
steering wheel pad.

3.

Using a service wire, connect P+ and P– on center
airbag sensor assembly and front passenger air-
bag assembly.

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.

2.

Using SST, connect terminals Tc and E

1

 of DLC2.

SST 09843–18020

3.

Check diagnostic trouble code.

Diagnostic trouble code 11 is not output.

Codes other than code 11 may be output at this time, but
this is not relevant to this check.

Replace center airbag sensor assembly.

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

RS–75

OK

NG

OK

NG

7

Check D squib.

C

OK

Hint

P

1.

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 11 is not output.

Codes other than code 11 may be output at this time, but
this is not relevant to this check.

Replace steering wheel pad.

8

Check P squib.

C

OK

Hint

P

1.

Turn ignition switch LOCK.

2.

Disconnect battery negative (–) terminal cable, and
wait at least 20 seconds.

3.

Connect front passenger airbag assembly (squib)
connector.

4.

Disconnect steering wheel pad (squib) connector.

5.

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.

4.

Check diagnostic trouble code.

Diagnostic trouble code 11 is not output.

Codes other than code 11 nay be output at this time, but
they are not relevant to this check.

Replace front passenger airbag assembly.

RS–76

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

OK

NG

OK

NG

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.

9

Check front airbag sensor.

C

OK

P

Disconnect front airbag sensor connector.

Measure resistance between each terminal of front air-
bag sensor.

Notice:



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



 Make sure the front airbag sensor connector is
properly connected.

Replace front airbag sensor.

Repair or replace harness or connector between center airbag sensor assembly and front airbag sen-
sor (See page 

RS–48

).

10

Check spiral cable.

C

OK

P

Disconnect connector between center airbag sensor
assembly and spiral cable.

Measure resistance between D+, D– on spiral cable
side of connector between spiral cable and steering
wheel pad and body ground.

Resistance:

1 M

 or Higher

Repair or replace spiral cable.

Repair or replace harness or connector between
center airbag sensor assembly and spiral cable.

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

RS–77

WIRING DIAGRAM

DTC

12

•

Short in Squib Circuit of Front Airbag Sensor Circuit 
(to B+)

•

Open in Front Airbag Sensor 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 satisfied.
The front airbag sensor detects the deceleration force in a frontal collision and is located in the front fender on
the left and right sides.
For details of the function of each component, see FUNCTION OF COMPONENTS on page 

RS–10

. Diagnostic

trouble code 12 is recorded when a B+ short is detected in the squib circuit or the front airbag sensor circuit.

DTC No.

Diagnosis

12



Short circuit in squib wire harness (to B+)



Squib malfunction



Short circuit in front airbag sensor +S wire harness (to B+)



Open circuit in RH and LH front airbag sensor harness.



Spiral cable malfunction



Center airbag sensor assembly malfunction

RS–78

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING