Lexus SC300 / Lexus SC400. Service manual - part 801

OK

NG

INSPECTION PROCEDURE

1

Preparation.

P

1.

Disconnect battery negative (–) terminal cable, and
wait at least 90 seconds.

2.

Remove steering wheel pad (See page 

RS–19

).

3.

Disconnect connectors of front passenger airbag
assembly (See page 

RS–32

).

Caution:

Store the steering wheel pad with the

surface facing upward.

2

Check front airbag sensor circuit (Measure resistance between terminals +SR and –SR, +SL
and –SL of center airbag sensor assembly connector.)

C

OK

P

Disconnect center airbag sensor assembly connector.

Measure resistance between terminals +SR and –SR,
+SL and –SL of harness side connector of center airbag
sensor assembly.

Resistance:

755 

 – 885 

Go to step 

.

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

RS–99

OK

NG

3

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–n on center
airbag sensor assembly side of connector between
center airbag sensor assembly and front passen-
ger airbag.

4.

Connect negative (–) terminal cable to battery, and
wait at least 2 seconds.

1.

Turn ignition switch AAC 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 15 is not output.

Code other than code 15 may be output at this time, but
this is not relevant to this check.

Replace 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.

RS–100

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

OK

NG

OK

NG

4

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.

5

Check harness between center airbag sensor assembly and front airbag sensor.

C

OK

P

5.

Disconnect center airbag sensor assembly con-
nector.

6.

Using service wires, connect +SR and –SR, +SL
and –SL on the wire harness side of the center air-
bag sensor assembly connector.

Measure resistance between terminals +SR and –SR,
+SL and –SL of harness side connector of front airbag
sensor.

Notice:

 

Lightly touch ohmmeter proves at position shown

in illustration.



 Make sure the front airbag sensor connector is

properly connected.

Resistance:

Below 1 

Repair or replace harness or connector between center
airbag sensor assembly and front airbag sensor. (See
page 

RS–48

).

Replace front airbag sensor connector (See page 

RS–48

).

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

RS–101

DTC

22

SRS Warning Light System Malfunction

CIRCUIT DESCRIPTION

The SRS warning light is located on the combination meter.
When the supplemental restraint system is normal, the SRS 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 supplemental restraint system, the SRS warning light lights up to inform the driver of the
abnormality.
When terminals Tc and E

1

 of the DLC2 are connected, the diagnostic trouble code is displayed by the blinking

of the SRS warning light.
The SRS 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 SRS warning light will not
light up.
Diagnostic trouble code 22 is recorded when a malfunction occurs in the SRS warning light system. If an OPEN
malfunction occurs in the SRS warning light system, the SRS warning light does not light up, so that until the
malfunction is repaired, the diagnostic trouble codes (including 22) cannot be confirmed.

DTC No.

Trouble Area

22



Open circuit in SRS warning light system.



Center airbag sensor assembly malfunction.

RS–102

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING