steering LEXUS SC400 1991 Service Owner's Manual

CONFIRM FUNCTIONING OF SST
When deploying the airbag, always use the specified SST:
SRS AIRBAG DEPLOYMENT TOOL.
SST 09082±00700
1. CONNECT SST TO BATTERY Connect the red clip of the SST to the battery positive (+) ter-
minal and the black clip to the battery negative (±) terminal.
HINT: Do not connect the yellow connector which connects
with the airbag system.
2. CONFIRM FUNCTIONING OF SST Press the SST activation switch, and confirm the LED of the
SST activation switch lights up.
CAUTION: If the LED lights up when the activation switch
is not being pressed, SST malfunction is probable, so
definitely do not use the SST.
±
SRS AIRBAG Disposal of Steering Wheel Pad (with Aribag)AB±97
WhereEverybodyKnowsYourName

SERVICE SPECIFICATIONS
SERVICE DATA
TerminalFront airbag sensor resistance

S ±
A755±885

S
A

S ± S
755 885



S ± ALess than 1

TORQUE SPECIFICATIONS
Part tightenedNVmkgf Vcmft Vlbf
Steering wheel3536026Steering wheel
Steering wheel pad
35
7.4
360
75
26
65 in. Vlbfg
Front airbag sensor25260 19g
Center airbag sensor assembly131309
AB±98±
SRS AIRBAG Disposal of Steering Wheel Pad (with Airbag)
WhereEverybodyKnowsYourName

GENERAL DESCRIPTION
The LEXUS SC400 is equipped with an SRS (Supplemental Restraint System) a\
irbag.
Failure to carry out service operations in the correct sequence could cause the\
airbag system to unex-
pectedly deploy during servicing, possibly leading to a serious accident.
Further, if a mistake is made in servicing the airbag system, it is possible the\
airbag may fail to operate
when required.
Before performing servicing (including removal or installation of parts, insp\
ection or replacement), be
sure to read the following items carefully, then follow the correct procedure described in the repair
manual.
1. Malfunction symptoms of the airbag system are difficult to confirm, so the diagnostic codes become themost important source of information when troubleshooting.
When troubleshooting the airbag system, always inspect the diagnostic co\
des before disconnecting the
battery (See page AB±25).
2. Work must be started after approx. 20 seconds or longer from the time the ig\
nition switch is turned to the LOCK position and the negative (±) terminal cable is disconnec\
ted from the battery. (The
airbag system is equipped with a back±up power source so that if work is sta\
rted within 20 seconds
of disconnecting the negative (±) terminal cable of the battery, the airbag may be deployed.)
When the negative (±) terminal cable is disconnected from the battery, memory of the clock and audio sys-
tems will be cancelled. So before starting work, make a record of the conten\
ts memorized by the audio
memory system. Then when work is finished, reset the audio systems as before a\
nd adjust the clock. When
the vehicle has power tilt and power telescopic steering, power seat, power \
outside rear view mirror and
power shoulder belt anchorage, which are all equipped with memory function, it\
is not possible to make
a record of the memory contents. So when the work is finished, it will be\
necessary to explain this fact to
the customer, and ask the customer to adjust the features and reset the memory. To avoid erasing the
memory of each memory system, never use a back±up power supply from outside\
the vehicle.
3. Even in cases of a minor collision where the airbag does not deploy, the front airbag sensors and
the steering wheel pad should be inspected (See page AB±9).
4. Never use airbag parts from another vehicle. When replacing parts, replace them with new parts.
5. Before repairs, remove the airbag sensors if shocks are likely to be applied to the sensors during repairs.
6. Never disassemble and repair the front airbag sensors, center airbag sensor a\
ssembly or steering
wheel pad in order to reuse it.
7. If the front airbag sensors, center airbag assembly or steering wheel pa\
d have been dropped, or if there are cracks, dents or other defects in the case, bracket or conn\
ector, replace them with new
ones.
8. Do not expose the front airbag sensors, center airbag sensor assembly or\
steering wheel pad directly to hot air or flames.
9. Use a volt/ohmmeter with high impedance (10 kW/V minimum) for troubleshoo\
ting of the electrical circuit.
10. Information labels are attached to the periphery of the airbag components. Follow t\
he instructions
on the notices.
11. After work on the airbag system is completed, perform the airbag warning\
light check (See page AB±30 ).
AB±2
SRS AIRBAG
± General Description
WhereEverybodyKnowsYourName

FRONT AIRBAG SENSOR
1. Never reuse the front airbag sensors involved in a collisionwhen the airbag has deployed. (Replace both the left and
right airbag sensors.)
2. Install the front airbag sensor with the arrow on the sensor facing toward the front of the vehicle.
3. The front airbag sensor set bolts have been anti±rust treated. When the sensor is removed, always replace the set bolts
with new ones.
4. The front airbag sensor is equipped with an electrical connection check mechanism. Be sur\
e to lock this mechanism securely when connecting the connector. If the connector is not securely locked, a malfunction
code will be detected by the diagnosis system (See page AB±7).
SPIRAL CABLE (in COMBINATION SWITCH)
The steering wheel must be fitted correctly to the steering column with the\
spiral cable at the neutral posi-
tion, otherwise cable disconnection and other troubles may result. Refer to pa\
ge AB±17 of this manual con-
cerning correct steering wheel installation.
STEERING WHEEL PAD (with AIRBAG)
1. When removing the steering wheel pad or handling a new steering wheel pad, it 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. And do not store a steering
wheel pad on top of another one. (Storing the pad with its me-
tallic surface up may lead to a serious accident if the airbag
inflates for some reason.)
2. Never measure the resistance of the airbag squib. (This may cause the airbag to deploy, which is very dangerous.)
AB±3SRS AIRBAG ± General Description
WhereEverybodyKnowsYourName

3. Grease should not be applied to the steering wheel pad and the pad should not b\
e cleaned with detergents
of any kind.
4. Store the steering wheel pad where the ambient temperature remains below 93 °C (200 °F), without high
humidity and away from electrical noise.
5. When using electric welding, first disconnect the airbag connector (yellow \
color and 2 pins) under the steering column near the combination switch connector before starting work.
6. When disposing of a vehicle or the steering wheel pad alone, the airbag shou\
ld be deployed using an SST before disposal (See page AB±91). Perform the operation in a place away from electrical noise.
CENTER AIRBAG SENSOR ASSEMBLY
The connector of the center airbag sensor assembly should be connected or d\
isconnected with the sensor
mounted on the floor. It the connector is connected or disconnected while the center airbag \
sensor assem-
bly is not mounted to the floor, it could cause undesired ignition of the airbag system.
WIRE HARNESS AND CONNECTOR
The airbag system wire harness is integrated with the cowl wire harness ass\
embly. The wires for the airbag
wire harness are encased in a yellow corrugated tube. All the connectors\
for the system are also a standard
yellow color. If the airbag system wire harness becomes disconnected or the connecto\
r becomes broken
due to an accident, etc., repair or replace it as shown on page AB±20.
AB±4
SRS AIRBAG
± General Description
WhereEverybodyKnowsYourName

OPERATION
FUNCTION OF COMPONENTS
1. FRONT AIRBAG SENSORA front airbag sensor is mounted inside each of the front
fenders. The sensor unit is a mechanical type. When the sen-
sor detects deceleration force above a predetermined limit in
a collision, the contacts in the sensor make contact, sending
a signal to the center airbag sensor assembly. The sensor
cannot be disassembled.
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. STEERING WHEEL PAD (with AIRBAG) The inflater and bag of the airbag system are stored in the
steering wheel pad 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. AIRBAG WARNING LIGHT The airbag 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
self±diagnosis. In normal operating condition when the igni-
tion switch is turned to the ACC or ON position, the light goes
on for about 6 seconds and then goes off.
5. CENTER AIRBAG SENSOR ASSEMBLY The center airbag sensor assembly is mounted on the floor
inside the center cluster. The center airbag sensor assembly
consists of a center airbag sensor, safing sensors, ignition
control and drive circuit, diagnosis circuit, etc. It receives sig-
nals f rom the airbag sensors, judges whether the airbag must
be activated or not and diagnoses system malfunctions. AB±5
± OperationSRS AIRBAG
WhereEverybodyKnowsYourName

(4) Connector Twin±Lock MechanismWith this mechanism connectors (male and female connectors) are locked by \
two locking devices to
increase connection reliability. If the primary lock is incomplete, ribs interfere and prevent the seco\
nd-
ary lock.
When the vehicle is involved in a frontal collision in the hatched area (Fi\
g. 1) and the shock is larger than a prede-
termined level, the airbag is activated automatically. Safing sensors are designed to go on at a smaller decelera-
tion rate than the front and center airbag sensors. As illustrated in Fig. 2\
below, ignition is caused when current
flows to the squib, which happens when a safing sensor and a front airbag sen\
sor and/or the center airbag sen-
sor go on simultaneously.
When a deceleration force acts on the sensors, it causes the squib to ignite\
. Gas is then generated, increasing
the pressure inside the bag rapidly. The inflated bag breaks open the steering wheel pad. Bag inflation then
ends, and the gas is discharged through discharge holes provided behind the b\
ag. The bag becomes deflated
as a result.
AB±8SRS AIRBAG ± Operation
WhereEverybodyKnowsYourName

INSPECTION ITEMS AND REPLACEMENT REQUIREMENTS
If a Vehicle is brought in for an airbag system inspection, or if a vehicle wh\
ich has been involved in a collision
is inspected, perform the inspection in accordance with the following proc\
edure. If any problems are discovered,
replace the affected part with a new one.
Steering Wheel Pad (with Airbag), Steering Wheel and Spiral
Cable
INSPECTION ITEMS
1. VEHICLES NOT INVOLVED IN A COLLISION(a) Perform a diagnostic system check (See page AB±30).
(b) Perform a visual check which includes the following items with the steering wheel pad (with airbag) installed in the vehicle.
w Check 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 AB±30).
(b) Perform a visual check which includes the following items with the steering wheel pad (with airbag) removed from the vehicle.
w Check 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 harnesses.
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 AB±14, ªREMOVAL AND INSTALLATIONº and be
sure to follow the correct procedure.
IF THE AIRBAG IS DEPLOYED
(a) Perform a diagnostic system check (See page AB±30).
(b) Perform a visual check which includes the following items with the steering wheel pad (with airbag) removed from the vehicle.
w Check for deformation of the horn button contact plate of
the steering wheel.
w Check for damage to the spiral cable connector and wire
harness.
AB±9SRS AIRBAG ± Inspection Items and Replacement Requirements
WhereEverybodyKnowsYourName

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 steeri\
ng wheel, and the
clearance should be uniform all the way around when the new steering wheel pad is\
installed on the
steering wheel.
REPLACEMENT REQUIREMENTS
In the following cases, replace the steering wheel pad, steering wheel or \
spiral cable.
CAUTION: For replacement of the steering wheel pad, see page AB±16, ªREMOVAL AND INSTALLA-
TIONº 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 t\
o be faulty during the check
in item 1±(b) or 2±(b).
w If the steering wheel pad has been dropped.
Front Airbag Sensor
INSPECTION ITEMS
1. VEHICLES NOT INVOLVED IN A COLLISION
w Perform a diagnostic system check (See page AB±30).
2. VEHICLES INVOLVED IN A COLLISION (a) Perform a diagnostic system check (See page AB±30).
(b) If the front fender of the car or its periphery is damaged, perform visual check for damage to the front airbag
sensor, which includes the following items even if the
airbag was not deployed:
w Bracket deformation.
w Peeling of paint from the bracket.
w Cracks, dents or chips in the case.
w Cracks and dents in, or chipping and scratches of
the connector.
w Peeling off of the label or damage to the series
number.
Also refer to the body dimension drawings on page
BO±133 and check the dimensions and mounting sur-
face angle of the body area where the front airbag sen-
sors are mounted.
AB±10SRS AIRBAG ± Inspection Items and Replacement Requirements
WhereEverybodyKnowsYourName

PREPARATION
SST (SPECIAL SERVICE TOOLS)
09082±00700SRS Airbag
Deployment Tool
09213±31021Crankshaft Pulley
Puller
09843±18020Diagnosis Check
Wiring
Steering wheel
RECOMMENDED TOOLS
09042±00010Torx Socket
T30
09042±00020Torx Socket
T30
09082±00015TOYOTA
Electrical Tester
Center airbag sensor assembly
Steering wheel pad
EQUIPMENT
Part NameNote
Torque wrench
AB±13SRS AIRBAG ± Preparation
WhereEverybodyKnowsYourName