Lexus SC300 / Lexus SC400. Service manual — part 793

DIAGNOSTIC TROUBLE CODE MATRIX CHART

If a malfunction code is displayed during the diagnostic trouble code check, check the circuit listed for that
code in the table below (Proceed to the page given for that circuit).

ÑÑÑÑÑ

ÑÑÑÑÑ

DTC No.

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Diagnosis

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

Page

ÑÑÑÑÑ

ÑÑÑÑÑ

(Normal)*

1

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Source voltage drop

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–68

ÑÑÑÑÑ

ÑÑÑÑÑ

11

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Short in squib circuit or front airbag sensor circuit (to ground)

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–70

ÑÑÑÑÑ

ÑÑÑÑÑ

12

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Short in squib circuit or front airbag sensor circuit (to B+)

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–78

ÑÑÑÑÑ

ÑÑÑÑÑ

13

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Short in squib circuit (between D+ wire harness and D– wire harness)

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–85

ÑÑÑÑÑ

ÑÑÑÑÑ

14

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Open in squib circuit (between D+ wire harness and D– wire harness)

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–92

ÑÑÑÑÑ

ÑÑÑÑÑ

15

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Open in front airbag sensor circuit

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–97

ÑÑÑÑÑ

ÑÑÑÑÑ

22*

2

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

SRS warning light system malfunction

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–102

ÑÑÑÑÑ

ÑÑÑÑÑ

31

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Center airbag sensor assembly malfunction

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–108

ÑÑÑÑÑ

ÑÑÑÑÑ

53

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Short in squib circuit (between P+ wire harness and P– wire harness)

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–110

ÑÑÑÑÑ

ÑÑÑÑÑ

54

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Open in squib circuit (between P+ wire harness and P– wire harness)

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

RS–115

HINT:
*

1

When the SRS warning light remains lit up and the diagnostic trouble code is the normal code, this means

a source voltage drop.
*

2

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 code (including 22) cannot be confirmed.

PROBLEM SYMPTOM CHART

Proceed with troubleshooting of each circuit in the table below.

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Problem Symptom

ÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑ

Inspection Item

ÑÑÑÑÑÑ

ÑÑÑÑÑÑ

Page

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

With the ignition switch at ACC or ON, the SRS warning light

sometimes lights up after approx. 6 seconds have elapsed

SRS warning light system

(Always lit up when ignition switch is

RS–119

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

SRS warning light lights up even when ignition switch is in

the LOCK position

(Always lit up when ignition switch is
LOCK position)

RS–119

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Diagnostic trouble code not displayed.

Tc terminal circuit

RS–121

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

ÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑÑ

Diagnostic trouble code continuously displayed.

Tc terminal circuit

RS–121

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

RS–67

WIRING DIAGRAM

CIRCUIT INSPECTION

DTC

(Normal) Source Voltage Drop

CIRCUIT DESCRIPTION

The supplemental restraint system is equipped with a voltage – increase circuit (DC–DC converter) in the center
airbag sensor assembly in case the source voltage drops.
When the battery voltage drops, the voltage – increase circuit (DC–DC converter) functions to increase the volt-
age of the supplemental restraint system to normal voltage.
The diagnosis system malfunction display for this circuit is different to other circuits – when the SRS warning
light remains lit up and the diagnostic trouble code is a normal code, source voltage drop is indicated. Malfunc-
tion in this circuit is not recorded in the center airbag sensor assembly, and approx. 10 seconds after the source
voltage returns to normal, the SRS warning light automatically goes off.

DTC No.

Diagnosis

(Normal)

Source voltage drop.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

(See page

CH–1

).

RS–68

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

YES

NO

INSPECTION PROCEDURE

1

Preparation.

P

1.

Turn ignition switch LOCK.

2.

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

3.

Connect battery negative (–) terminal cable.

4.

Disconnect center airbag sensor assembly con-
nector.

5.

Turn ignition switch ON. But do not start engine.

6.

Measure voltage at IG

2

or ACC on connector wire

harness side of center airbag sensor assembly and
operate electric system (defogger, wiper, headlight,
heater blower, etc.)
Voltage: 6 V – 11.5 V at IG

2

and ACC.

7.

Turn electric system switch OFF.

8.

Turn ignition switch LOCK.

9.

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

10. Remove voltmeter and connect center airbag sen-

sor assembly connector.

11. Connect battery negative (–) terminal cable.

2

Does SRS warning light turn off after approx. 10 seconds?

C

P

Turn ignition switch ACC or ON and wait at least 20 sec-
onds.

Clear malfunction code. Turn ignition switch LOCK and
wait at least 20 seconds.

Operate electric system checked in

(5) and check

that SRS warning light goes off after approx. 10 sec-
onds.

Check diagnostic trouble code, and if a malfunction code
is output, perform trouble shooting according to mal-
function code. If a normal code is output, replace center
airbag sensor assembly.

Check battery and charging system.
(See page

CH–1

)

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING

RS–69

DTC

11

Short in Squib Circuit or Front Airbag Sen-
sor Circuit (to Ground)

CIRCUIT DESCRIPTION

The squib circuit consists of the center airbag sensor assembly, spiral cable and the steering wheel pad (squib),
wire harness connector and front passenger airbag assembly (squib). It causes the SRS to operate when the
SRS operation 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 11 is recorded when occurrence of ground short is detected in the squib circuit or front airbag sen-
sor circuit.

DTC No.

Diagnosis

11

Short circuit in squib wire harness (to ground)

Squib malfunction

Short circuit in front airbag sensor +S, D

+

, D–, P+, P– wire harness (to ground).

Front airbag sensor malfunctions.

Short circuit between +S wire harness and –S wire harness of front airbag sensor.

Spiral cable malfunction.

Center airbag sensor assembly malfunction.

RS–70

–

SUPPLEMENTAL RESTRAINT SYSTEM

TROUBLESHOOTING