Lexus SC300 / Lexus SC400. Service manual - part 775

Tc Terminal Circuit

CIRCUIT DESCRIPTION

By connecting terminal Tc and E

1

 of the DLC1 or DLC2, the center airbag sensor assembly is set in the diagnos-

tic trouble code output mode. The diagnostic trouble codes are displayed by the blinking of the SRS warning
light.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Troubleshooting  for this system is different depending on whether the diagnostic trouble code is not displayed
SRS warning light is always lit up with a DTC check procedure, or is displayed without a DTC check procedure.
Confirm the problem symptoms first before selecting the appropriate troubleshooting procedure.
HINT: If the diagnostic trouble code is not displayed or SRS warning light is always lit up with a DTC check proce-
dure perform the following troubleshooting:

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

RS–121

WIRING DIAGRAM

DIAGNOSTIC CHART

DIAGNOSTIC CHART

RS–122

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

NG

OK

NG

OK

INSPECTION PROCEDURE

HINT: If the diagnostic trouble code is not displayed, perform the following troubleshooting:

1

Check voltage between terminals Tc and E

1

 of DLC1 or DLC2.

C

OK

P

Turn ignition switch ACC or ON.

Measure voltage between terminals Tc and E

1

 of DLC1

or DLC2.

Voltage:

Battery positive voltage

Go to step 

.

2

Check voltage between terminal Tc of DLC1 or DLC2 and body ground.

C

OK

Measure voltage between terminal Tc of DLC1 or DLC2
and body ground.

Voltage:

Battery positive voltage

Check harness between terminal E1 of DLC1 or DLC2
and body ground.

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

RS–123

NG

OK

3

Check center airbag sensor assembly.

C

OK

P

1.

Turn ignition switch LOCK.

2.

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

3.

Remove steering wheel pad (See page 

RS–19)

.

4.

Disconnect connectors of front passenger airbag
assembly (See page 

RS–32)

.

Check operation of SRS warning light.

SRS warning light comes on.

Check harness between center airbag sensor assembly
and DLC1 or DLC2.

Replace center airbag sensor assembly.

RS–124

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING