Lexus SC300 / Lexus SC400. Manual - part 48

MEMO

–

SRS AIRBAG

Troubleshooting

AB–73

Diag. Code 22

Airbag Warning Light System Malfunction

      CIRCUIT DESCRIPTION

The airbag warning light is located on the combination meter.
When the airbag system is normal, the airbag warning light lights 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 airbag system, the airbag warning light lights up to inform the driver of
the abnormality.
When terminals Tc and E of the TDCL are connected, the diagnostic code is displayed by the blinking
of the airbag warning light.
The airbag warning light circuit is equipped with an electrical connection check mechanism which 
detects when the connector to the center airbag sensor assembly is not properly connected.
If the connector to the center airbag sensor assembly is not properly connected, the airbag warning
light will not light up.
Diagnostic code 22 is recorded when a malfunction occurs in the airbag warning light system.
If an OPEN malfunction occurs in the airbag warning light system, the airbag warning light does not
light up, so that until the malfunction is repaired, the diagnostic codes (including code 22) cannot be
confirmed.

Code No.

Diagnosis

22

 Open circuit in airbag warning light system.

22

 Center airbag sensor assembly malfunction.

AB–74

–

SRS AIRBAG

Troubleshooting

OK

NG

1

2

3

4

5

6

6

OK

OK

YES

YES

NG

NG

NO

NO

Check connection of center airbag sensor
assembly connector.

Preparation.

Check airbag warning light circuit.

Does airbag warning light come on?

Is new ECU –B fuse burnt out again?

GO to step

Repair.

Repair airbag warning light circuit

(See page 

BE–150

).

Check terminal LA of center
airbag sensor assembly and
electrical connection check
mechanism. If normal, replace
center airbag sensor assembly.

Using simulation method,
reproduce malfunction symptoms

(See page 

IN–20

).

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

Check ECU –B fuse.

      DIAGNOSTIC CHART

Troubleshooting  for this system is different for when the airbag warning light does not light up and for
when diagnostic code 22 is output. Confirm the problem symptoms first before selecting the appropriate
troubleshooting  procedure.
HINT: If airbag warning light does not light up, perform the following troubleshooting:

–

SRS AIRBAG

Troubleshooting

AB–75

YES

NO

1

Replace center airbag sensor assembly.

Using simulation method,
reproduce malfunction symptoms

(See page 

IN–20

).

WIRING DIAGRAM

Is diagnostic code 22 output again?

      DIAGNOSTIC CHART

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

AB–76

–

SRS AIRBAG

Troubleshooting