Lexus SC300 / Lexus SC400. Service manual — part 49

Check ECU–B fuse.

NG

OK

1

6

Go 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

OK

Repair.

Check connection of center airbag sensor assembly connector.

2

3

Preparation.

INSPECTION PROCEDURE

HINT: If airbag warning light does not light up, perform the following troubleshooting:

–

SRS AIRBAG

Troubleshooting

AB–77

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 normal. To
make sure of this, use the simulation method to check.

Check harness between ECU–B fuse and airbag warning light, and ECU–B fuse and center airbag sensor
assembly.

AB–78

–

SRS AIRBAG

Troubleshooting

1

Using simulation method, reproduce malfunction

symptoms (See page

IN–20

).

NO

YES

(1)

Turn ignition switch LOCK, and wait at least 2
seconds.

(2)

Turn ignition switch ACC or ON, and wait at least
20 seconds.

(3)

Using SST, connect terminals Tc and E

1

of TDCL.

SST 09843–18020

(4)

Check diagnostic code.

Clear malfunction code 41 stored in memory

(See page

AB–35

).

Is diagnostic code 22 output again?

Replace center airbag sensor assembly.

HINT: If diagnostic code 22 is output, perform the following troubleshooting:

–

SRS AIRBAG

Troubleshooting

AB–79

YES

Is diagnostic code 31 output again?

NO

1

Replace center airbag sensor assembly.

Using simulation method, reproduce
malfunction symptoms

(See page

IN–20

).

Diag. Code 31

Center Airbag Sensor Assembly Malfunction

CIRCUIT DESCRIPTION

The center airbag sensor assembly consists of a center airbag sensor, safing sensors, ignition control
and drive circuit, diagnosis circuit, etc.
It receives signals from the airbag sensors, judges whether or not the airbag must be activated, and
diagnoses system malfunction.
Diagnostic code 31 is recorded when occurrence of a malfunction in the center airbag sensor assembly
is detected.

Code No.

Diagnosis

31

Center airbag sensor assembly malfunction.

DIAGNOSTIC CHART

HINT: When a malfunction code other than code 31 is displayed at the same time, first repair the
malfunction indicated by the malfunction code other than code 31.

AB–80

–

SRS AIRBAG

Troubleshooting