1991 LEXUS SC400 steering

OPERATION
FUNCTION OF COMPONENTS
RS02M±04
1. STEERING WHEEL PAD (with AIRBAG)The inflater and bag of the supplemental restraint system are
stored in the steering wheel pad and cannot be disas-
sembled. The inflater contains a squib, igniter charge, gas
generant, etc., and inflates the bag in case of frontal collision.
2. SPIRAL CABLE (in COMBINATION SWITCH) A spiral cable is used as an electrical joint from the vehicle
body side to the steering wheel.
3. FRONT PASSENGER AIRBAG ASSEMBLY The inflater and bag of the supplemental restraint system are
stored in the front passenger airbag assembly and cannot be
disassembled.
The inflater contains a squib, igniter charge, gas generant,
etc., and inflates the bag in case of a frontal collision.
4. SRS WARNING LIGHT The SRS warning light is located on the combination meter.
It goes on to alert the driver of trouble in the system when a
malfunction is detected in the center airbag sensor assembly.
In normal operating conditions when the ignition switch is
turned to the ACC or ON position, the light goes on for about
6 seconds and then goes off.
5. FRONT AIRBAG SENSOR A front airbag sensor is mounted inside each of the front fend-
ers. The sensor unit is a mechanical type. When the sensor
detects deceleration force above a predetermined limit, con-
tacts is m ade in the sensor, sending a signal to the center air-
bag sensor assembly. The sensor cannot be disassembled.
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SUPPLEMENTAL RESTRAINT SYSTEM OPERATIONRS±9
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When the vehicle is involved in a frontal collision in the
hatched area (Fig. 1) and the shock is larger than a predeter-
mined level, the SRS is activated automatically. A safing sen-
sor is designed to go on at a smaller deceleration rate than
the front and center airbag sensors. As illustrated in Fig. 2,
ignition is caused when current flows to the squib, which hap-
pens when a safing sensor and a front airbag sensor and/or
the center airbag sensor go on simultaneously. When a de-
celeration force acts on the sensors, two squibs in the driver
airbag and front passenger airbag ignite and generate gas.
The gas discharging into the driver and front passenger air-
bags rapidly increases the pressure inside the bags breaking
open the steering wheel pad and instrument panel door.
Bag inflation then ends, and the bags deflate as the gas is
discharged through discharge holes at the bag's rear or side.
RS±14±
SUPPLEMENTAL RESTRAINT SYSTEM OPERATION
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STEERING WHEEL PAD AND
SPIRAL CABLE
INSPECTION ITEMS
RS04B±01
1. VEHICLES NOT INVOLVED IN A COLLISION
(a) Perform diagnostic system check. (See page RS±59)
(b) Perform a visual check which includes the following items with the steering wheel pad (with airbag installed in the
vehicle.
wCheck for cuts, minute cracks or marked discoloration
of the steering wheel pad top surface and grooved
portion.
2. VEHICLES INVOLVED IN A COLLISION IF THE AIRBAG IS NOT DEPLOYED
(a) Perform a diagnostic system check. (See page RS±59)
(b) Perform a visual check which includes the following items with the steering wheel pad (with airbag) removed from the
vehicle.
wCheck for cuts or cracks in, or marked discoloration of
the steering wheel pad top surface and grooved portion.
w Check for cuts and cracks in, or chipping of connectors
and wire harness.
w Check for deformation of the horn button contact plate
of the steering wheel.
HINT:
w If the horn button contact plate of the steering wheel is
deformed, never repair it. Always replace the steering
wheel assembly with a new one.
w There should be no interference between the steering
wheel pad and the steering wheel, and the clearance
should be uniform all the way around when the new
steering wheel pad is installed on the steering wheel.
CAUTION: For removal and installation of the steering
wheel pad, see page RS±18, ªSTEERING WHEEL PAD
AND SPIRAL CABLE REMOVAL AND INSTALLATIONº
and be sure to follow the correct procedure.
RS±16
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IF THE AIRBAG IS DEPLOYED
(a) Perform a diagnostic system check. (See page RS±59)
(b) Perform a visual check which includes the following items
with the steering wheel pad (with airbag) removed from he
vehicle.
wCheck for deformation of the horn button contact plate
of the steering wheel.
w Check for damage to the spiral cable connector and wire
harness.
HINT:
w If the horn button contact plate of the steering wheel is
deformed, never repair it. Always replace the steering
wheel assembly with a new one.
w There should be no interference between the steering
wheel pad and the steering wheel, and the clearance
should be uniform all the way around when the new
steering pad is installed on the steering wheel.
REPLACEMENT REQUIREMENTS
RS011±02
In the following cases, replace the steering wheel pad, steer-
ing wheel or spiral cable.
CAUTION: For replacement of the steering wheel pad,
see page RS±18, ªSTEERING WHEEL PAD AND SPIRAL
CABLE REMOVAL AND INSTALLATIONº and be sure to
follow the correct procedure.
w If the airbag has been deployed.
w If the steering wheel pad or spiral cable has been found
to be faulty in troubleshooting.
w If the steering wheel pad, steering wheel or spiral cable
has been found to be faulty during the check in item
1±(b) or 2±(b).
w If the steering wheel pad has been dropped.
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SUPPLEMENTAL RESTRAINT SYSTEM STEERING WHEEL PAD AND SPIRAL CABLERS±17
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COMPONENTS
RS04D±01
STEERING WHEEL PAD AND SPIRAL
CABLE REMOVAL AND INSTALLATION
RS04D±01
NOTICE:
wIf the wiring connector of the supplemental restraint
system is disconnected with the ignition switch at ON or
ACC, diagnostic trouble codes will be recorded.
w Never use SRS parts from another vehicle. When
replacing parts, replace with new parts.
1. DISCONNECT NEGATIVE (±) TERMINAL CABLE FROM
BATTERY
CAUTION: Work must be started after 90 seconds from
the time the ignition switch is turned to the LOCK posi-
tion and the negative (±) terminal cable is disconnected
from the battery (See page RS±2).
RS±18
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2. REMOVE STEERING WHEEL PAD
(a) Place the front wheels facing straight ahead.
(b) Using a torx wrench, loosen the 4 screws. Torx wrench: T30(Part No. 09042±00010 or locally manufactured tool)
(d) Loosen the torx screws until the groove along the screw circumference catches on the screw case.
(e) P u l l t h e w heel pad out from the steering wheel and
disconnect the SRS connector.
NOTICE: When removing the wheel pad, take care not to
pull the airbag wire harness.
CAUTION:
w When storing the wheel pad, keep the upper surface of
the pad facing upward (See pages RS±3).
w Never disassemble the wheel pad.
3. REMOVE STEERING WHEEL
(a) Disconnect the connector.
(b) Remove the set nut.
(c) Place matchmarks on the steering wheel and main shaft.
(d) Using SST, remove the steering wheel.
SST 09213±31021
4. REMOVE AND INSTALL SPIRAL CABLE FROM/TO COMBINATION SWITCH
(See page BE±51)
NOTICE: Do not disassemble the spiral cable or apply oil
to it.
5. CENTER SPIRAL CABLE
(a) Check that the front wheels are facing straight ahead.
(b) Turn the spiral cable c ounterclockwise by hand until it
becomes harder to turn the cable.
(c) Then rotate the spiral cable clockwise about 3 turns to align the red mark.
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SUPPLEMENTAL RESTRAINT SYSTEM STEERING WHEEL PAD AND SPIRAL CABLERS±19
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6. INSTALL STEERING WHEEL
(a) Align matchmarks on the steering wheel and main shaft, andinstall the steering wheel to the main shaft.
(b) Install and torque the set nut.
Torque: 35 N Vm (360 kgf Vcm, 26 ft Vlbf)
(c) Connect the connector.
7. INSTALL STEERING WHEEL PAD
(a) Connect the SRS connector.
(b) Install the wheel pad after confirming that the circumference
groove of the torx screws is caught on the screw case.
(c) Using a torx wrench, tighten the 4 screws.
Torque: 7.4 N Vm (75 kgf Vcm, 65 in. Vlbf)
NOTICE:
w Make sure the wheel pad is installed to the specified
torque.
w If the wheel pad has been dropped, or there are cracks,
dents or other defects in the case or connector, replace
the wheel pad with a new one.
w When installing the wheel pad, take care that the wirings
do not interfere with other parts and are not pinched
between other parts.
8. CHECK STEERING WHEEL CENTER POINT
9. CONNECT NEGATIVE (±) TERMINAL CABLE TO
BATTERY
RS±20
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SUPPLEMENTAL RESTRAINT SYSTEM STEERING WHEEL PAD AND SPIRAL CABLE
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STEERING WHEEL PAD (WITH AIRBAG)
DISPOSAL
RS04E±01
When scrapping vehicles equipped with a supplemental re-
straint system or disposing of a steering wheel pad (with air-
bag), always first deploy the airbag in accordance with the
procedure described below.
If any abnormality occurs with the airbag deployment, con-
tact the SERVICE DEPT. of TOYOTA MOTOR SALES,
U.S.A., INC..
Never dispose of a steering wheel pad which has an un-
deployed airbag.
When disposing of a steering wheel pad with an airbag
deployed in a collision, follow the same procedure given un-
der ªWhen scrapping vehicle, step 5. DISPOSAL OF STEER-
ING WHEEL PAD (WITH AIRBAG)º (See page RS±23).
PRECAUTIONS FOR AIRBAG DEPLOYMENT
w The airbag produces a sizeable exploding sound when
it deploys, so perform the operation out±of±doors and
where it will not create a nuisance to nearby residents.
w When deploying the airbag, always use the specified
SST; SRS AIRBAG DEPLOYMENT TOOL (SST
09082±00700). Perform the operation in a place away
from electrical noise.
w When deploying an airbag, perform the operation from
at least 10 m (33 ft) away from the steering wheel pad.
w The steering wheel pad is very hot when the airbag is
deployed, so leave it alone for at least 30 minutes after
deployment.
w Use gloves and safety glasses when handling a steering
wheel pad with deployed airbag.
w Always wash your hands with water after completing the
operation.
w Do not apply water, etc. to a steering wheel pad with
deployed airbag.
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SUPPLEMENTAL RESTRAINT SYSTEM STEERING WHEEL PAD AND SPIRAL CABLERS±21
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