1991 LEXUS SC400 steering wheel

(1) Turn ignition switch LOCK.
(2) Disconnect negative (±) terminal cable frombattery.
(3) Connect connector to center airbag sensor assembly.
(4) Using a service wire, Connect D
+ and D± on
spiral cable side of connector between spiral
cable and steering wheel pad.
(5) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
Check squib circuit.
Codes other than code 12 may be output at this
time, but this is not relevant.
Measure voltage at D+ on spiral cable side of con-
nector between spiral cable and steering wheel
pad.
Go to step [ 7 ].
Resistance: 1 V
Replace center airbag sensor assembly.
Check center airbag sensor assembly.
(1) Turn ignition switch ACC or ON and wait at least 20 seconds.
(2) Using SST, connect terminals Tc and E
1 of
TDCL.
SST 09843±18020
(3) Check diagnostic code.
Diagnostic code 12 is not output. AB±51
SRS AIRBAG
± Troubleshooting
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(1) Turn ignition switch LOCK.
(2) Disconnect battery negative (±) terminal cable,and wait at least 20 seconds.
(3) Connect steering wheel pad (squib) connector.
(4) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
Check squib.
Measure voltage at D+ on spiral cable side of con-
nector between spiral cable and steering wheel
pad.
Repair or replace spiral cable.
Diagnostic code 12 is not output.
Replace steering wheel pad.
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.
Repair or replace harness or connector between center airbag sensor assembly a\
nd spiral cable.
Check spiral cable.
(1) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(2) Using SST, connect terminals Tc and E
1 of
TDCL.
SST 09843±18020
(3) Check diagnostic code.
Codes other than code 12 may be output at this
time, but this is not relevant.
Voltage: Below 1 V
(1) Turn ignition switch LOCK.
(2) Disconnect connector between center airbag sensor assembly and spiral cable.
(3) Turn ignition switch ON.
AB±52
SRS AIRBAG
± Troubleshooting
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Diag. Code 13Short in Squib Circuit (Between D+ Wire
Harness and D± Wire Harness)
CIRCUIT DESCRIPTION
The squib circuit consists of the center airbag sensor assembly, spiral cable and the steering wheel
pad (squib). It causes the airbag to deploy when the airbag deployment\
conditions are satisfied.
For details of the function of each component, see FUNCTION OF COMPONENT\
S on page AB±7.
Diagnostic code 13 is recorded when a short is detected in the D+ wire harness and\
D± wire harness
of the squib circuit.
Code No.
Diagnosis
13

Short circuit between D+ wire harness and D± wire harness of squib.

Squib malfunction.

Spiral cable malfunction.

Center airbag sensor assembly malfunction.
DIAGNOSTIC CHART
Preparation.
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 squib circuit.
Check center airbag sensor assembly.
Check squib.
Go to step [ 5 ] on next page.
Replace center airbag sensor
assembly.
Replace steering wheel pad.
AB±54SRS AIRBAG ± Troubleshooting
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INSPECTION PROCEDURE
(1) Disconnect battery negative (±) terminal cable,and wait at least 20 seconds.
(2) Remove steering wheel pad (See page AB±14).
Preparation.
Measure resistance between D+ and D± on spiral
cable side of connector between spiral cable and
steering wheel pad.
Go to step [ 5 ].
When storing steering wheel pad, keep upper
surface of the pad facing upward.
Resistance: 1 k
or higher
Check squib circuit.
AB±56SRS AIRBAG ± Troubleshooting
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(1) Connect negative (±) terminal cable to battery.
(2) Clear malfunction code 41 stored in memory(See page AB±32).
Check center airbag sensor assembly.
Replace center airbag sensor assembly.
(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.
Codes other than code 13 may be output at this
time, but this is not relevant to this check.
Diagnostic code 13 is not output.
(1) Turn ignition switch LOCK.
(2) Disconnect battery negative (±) terminal cable, and wait at least 2 seconds.
(3) Connect steering wheel pad (squib) connector.
(4) Connect negative (±) terminal cable to battery.
(5) Clear malfunction code 41 stored in memory
(See page AB±32).
Check squib.
Replace steering wheel pad.
Codes other than code 13 may be output at this
time, but this is not relevant to this check.
Diagnostic code 13 is not output.
(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.
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. AB±57
SRS AIRBAG
± Troubleshooting
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(1) Disconnect connector between center airbagsensor assembly and spiral cable.
(2) Release airbag activation prevention mecha- nism on center airbag sensor assembly side of
spiral cable connector (See page AB±60).
Check squib.
Resistance: 1 M
or higher
Repair or replace spiral cable.
Measure resistance between D+ and D± on spiral
cable side of connector between spiral cable and
steering wheel pad.
(1) Disconnect center airbag sensor assembly connector.
(2) Release airbag activation prevention mecha- nism on center airbag sensor assembly connec-
tor (See page AB±60).
Check harness between center airbag sensor assembly and spiral cable.
Resistance: 1 M
or higher
Repair or replace harness or connector
between center airbag sensor assembly and
spiral cable.
Measure resistance between D+ and D± on center
airbag sensor assembly side of connector between
center airbag sensor assembly and spiral cable.
AB±58
SRS AIRBAG
± Troubleshooting
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REMOVAL OF INSTRUMENT PANEL
(See page BO±108)
1. TILT DOWN AND PULL OUT STEERING WHEEL
2. DISCONNECT BATTERY CABLE FROM NEGATIVE TERMINAL
CAUTION: Work must be started after approx. 20 seconds or
longer from the time the ignition switch is turned to the
ºLOCKº position and the negative (±) terminal cable is discon-
nected from the battery.
3. REMOVE RIGHT AND LEFT FRONT PILLAR GARNISH(See step 2 on page BO±122)
4. REMOVE STEERING WHEEL (See step 1 on page SR±7)
NOTICE: The steering wheel pad should be placed with
the pad top surface facing up.
5. REMOVE STEERING COLUMN COVER Remove three screws and the cover.
6. REMOVE SHIFT LEVER NOB (a) Slide the shaft collar downward and remove two screws.
(b) Remove the nob.
7. REMOVE UPPER CONSOLE PANEL REAR (a) Open the ash tray lid.
(b) Lift the console panel toward you.
(c) Insert your finger in the shift lever groove and pull theconsole panel upward away from you.
(d) Remove the panel.
8. REMOVE CUP HOLDER (a) Open the cup holder lid.
(b) Pull up the holder.
NOTICE: Do not pull the lid.
9. REMOVE UPPER CONSOLE PANEL Remove six screws and pry out of the panel.
BO±110
±
BODY Instrument Panel
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SRS AIRBAG
(See page AB±2)
The LEXUS SC300 is equipped with an SRS (Supplemental Restraint System)\
airbag.
Failure to carry out service operations in the correct sequence could cause the airbag system to deploy,
possibly leading to a serious accident.
When removal or installation of airbag parts and the yellow wire harness\
and connector for the airbag is
necessary, refer to the precautionary notices in the AB section before performing\
the operation.

Work must be started after 20 seconds or longer from the time the ignition switch is set to the LOCK
position and the negative (±) terminal cable is disconnected from the batte\
ry.
(The airbag system is equipped with a back±up power source so that if wor\
k is started within 20 se-
conds of disconnecting the negative (±) terminal cable of the batte\
ry, the airbag may be deployed.

To avoid erasing the memory of each memory system, never use a back±up power supply from
outside the vehicle.

Before repairs, remove the airbag sensors if shocks are likely to be applied t\
o the sensors during
repaires.

The front airbag sensor set bolt has been anti±rust treated. When the\
sensor is removed, always
replace the set bolt with a new one.

If the front airbag sensors, center airbag sensor or steering wheel pad ha\
ve been dropped, or if there
are cracks, dents or other defects in the case, bracket or connector, replace them with new ones.

Never use airbag parts from another vehicle. When replacing parts, repla\
ce them with new parts.

Do not expose the front airbag sensors, center airbag sensor or steering w\
heel pad directly to hot air
or flames.

The airbag system's wire harness is integrated with the cowl wire harness assembly. The wires for the
airbag wire harness are encased in a yellow corrugated tube. All the connector\
s for the system are
also a standard yellow color. If the airbag system wire harness becomes disconnected or the
connector becomes broken due to an accident, etc., repair or replace it as shown \
on page AB±20.

The steering wheel must be fitted correctly to the steering column with the\
spiral cable at the neutral
position; otherwise, cable disconnection and other troubles may result. \
Refer to page AB±14 of this
manual concerning correct steering wheel installation.

When removing the steering wheel pad or handling a new steering wheel pad, i\
t should be placed with
the pad top surface facing up. In this case, the twin±lock type connector lock lever should be in the
locked state and care should be taken to place it so the connector will not be damaged. (\
Storing the
pad with its metallic surface up may lead to a serious accident if the a\
irbag inflates for some reason.)

Grease should not be applied to the steering wheel pad and the pad should not \
be cleaned with
detergents of any kind.

Store the steering wheel pad where the ambient temperature remains below 93 C (200 F), without
high humidity and away from electrical noise.

Information labels are attached to the periphery of the airbag component\
s. Follow the notices.

When the ignition switch is at ACC or ON and the airbag warning light remains on, the cent\
er airbag
sensor assembly has detected a malfunction code. (See page AB±30).
BO±8
±
BODY General Information
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