1991 LEXUS SC300 shock

When the negative (±) terminal cable is disconnected from
the battery, memory of the clock and audio systems will be
cancelled. So before starting work, make a record of the con-
tents memorized by each memory system. Then when work
is finished, reset the clock and audio systems as before.
When the vehicle has power tilt and power telescopic steer-
ing, 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 operation 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. The center airbag sensor assembly contains mercury. After
performing replacement, do not destroy the old part. When
scrapping the vehicle or replacing the center airbag sensor
assembly itself, remove the center airbag sensor assembly
and dispose of it as toxic waste.
7. Never disassemble and repair the front airbag sensors, center airbag sensor assembly or steering wheel pad in order
to reuse it.
8. If the front airbag sensors, center airbag sensor assembly or steering wheel pad have been dropped, or if there are cracks,
dents or other defects in the case, bracket or connector,
replace them with new ones.
9. Do not expose the front airbag sensors, center airbag sensor assembly or steering wheel pad directly to hot air or flames.
10. U s e a v o l t / o h m m e t e r w i t h h i g h i m pedance (10 kW/V
minimum) for troubleshooting of the electrical circuit.
11. Information labels are attached to the periphery of the airbag components. Follow the notices.
12. After work on the airbag system is completed, perform the
airbag warning light check (See page AB±30).
±
INTRODUCTION Precautions for Vehicles Equipped with SRS AirbagIN±9
WhereEverybodyKnowsYourName

wDo not perform repeat evacuation of system
5. USE CHARING CYLINDER TO CHARGE PROPER
AMOUNT OF REFRIGERANT
To prevent excessive use of refrigerant due to overcharging,
use a charging cylinder to charge the proper amount of refrig-
erant.
Handling Precautions for Refrigerant
1. DO NOT HANDLE REFRIGERANT IN AN ENCLOSED
AREA OR NEAR AN OPEN FLAME
2. ALWAYS WEAR EYE PROTECTION
3. BE CAREFUL THAT LIQUID REFRIGERANT DOES NOT GET IN YOUR EYES OR ON YOUR SKIN
If liquid refrigerant gets in your eyes or on your skin:
(a) Wash the area with lots of cool water.
CAUTION: Do not rub your eyes or skin.
(b) Apply clean petroleum jelly to the skin.
(c) G o i m m e d i a t e l y t o a p h y s i c i a n o r h o s p i t a l f o rprofessional treatment.
CAUTION: Do not attempt to treat yourself.
Handling Precautions for Refrigerant
Container
1. NEVER HEAT CONTAINER OR EXPOSE IT TO NAKED FLAME
2. BE CAREFUL NOT TO DROP CONTAINER AND NOT TO APPLY PHYSICAL SHOCKS TO IT
±
AIR CONDITIONING SYSTEM General DescriptionAC±3
WhereEverybodyKnowsYourName

3.14 X (Diameter)2
4
3. FIX STEERING WHEEL PAD TO DISC WHEEL WITH TIRE(a) Install bolts with washers in the four bolt holes in thesteering wheel pad.
Bolt: L 35.0 mm (1.4 in.) M 6.0 mm
Pitch 1.0 mm
NOTICE: Tighten the bolts by hand until the bolts
become difficult to turn.
Do not tighten the bolts too much.
(b) Using a service±purpose wire harness for vehicle, tie down the steering wheel pad to the disc wheel.
Wire harness: Stripped wire harness section 1.25 mm or
more (0.002 in. or more)
HINT: To calculate the square of the stripped wire harness
section ±
Square =
CAUTION: If a wire harness which is too thin or some oth-
er thing is used to tie down the steering wheel pad, it may
be snapped by the shock when the airbag is deployed,
this is highly dangerous. Always use a wire harness for
vehicle use which is at least 1.25 mm (0.002 in.).
(c) Using 3 wire harnesses, wrap the wire harnesses at least 2 times each around the bolts installed on the left
and right sides of the steering wheel pad.
CAUTION: Tightly wind the wire harness around the bolts
so that there is no slack.
If there is slackness in the wire harness, the steering
wheel pad may come loose due to the shock when the
airbag is deployed, this is highly dangerous.
(d) Face the upper surface of the steering wheel pad upward. Separately tie the left and right sides of the steering
wheel pad to the disc wheel through the hub nut holes.
Position the steering wheel pad connector so that it
hangs downward through a hub hole in the disc wheel.
CAUTION:
wMake sure that the wire harness is tight. It is very
dangerous if looseness in the wire harness results
in the steering wheel pad coming free through the
shock of the airbag deploying.
AB±94
±
SRS AIRBAG Disposal of Steering Wheel Pad (with Aribag)
WhereEverybodyKnowsYourName

wAlways tie down the steering wheel pad with the pad
side facing upward. It is very dangerous if the steer-
ing wheel pad is tied down with the metal surface
facing upward as the wire harness will be cut by the
shock of the airbag deploying and the steering
wheel pad will be thrown into the air.
HINT:
w The disc wheel will be marked by airbag deployment, so
use a redundant disc wheel.
4. CONFIRM FUNCTIONING OF SST (SEE PAGE AB±94)
SST 09082±0700
5. INSTALL SST CAUTION: Place the disc wheel on level ground.
(a) Connect the SST connector to the steering wheel pad
connector.
SST 09082±00700
NOTICE: To avoid damaging the SST connector and wire
harness, do not lock the secondary lock of the twin lock.
Also, provide some slack for the SST wire harness inside
the disc wheel.
(b) Move the SST to at least 10 m (33 ft) away from the steering wheel pad tied down on the disc wheel.
6. COVER STEERING WHEEL PAD WITH CARDBOARD BOX OR TIRES
(Covering Method Using Cardboard Box)
Cover the steering wheel pad with the cardboard box and
weigh the cardboard box down in four places with a at least
20 kg (44 lb, 196 N).
Size of cardboard box: Must exceed the following dimen-
sions ±x = 460 mm (18.11 in.)
When dimension y of the cardboard box exceeds
the diameter of the disc wheel with tire the steering
wheel pad is tied to±
x = 460 mm (18.11 in.) + width of tire
y = 650 mm (25.59 in.)
NOTICE: If a cardboard box smaller than the size speci-
fied is used, the cardboard box will be broken by the
shock of the airbag deployment.
±
SRS AIRBAG Disposal of Steering Wheel Pad (with Aribag)AB±95
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

(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

Description
The SRS (Supplemental Restraint System) airbag, together with
the seat belt, is designed to help protect the driver. In a collision,
the airbag sensors detect the shock, and if the front±to±rear shock
is greater than a specified value, an airbag stored in the steering
wheel pad is inflated instantaneously to help reduce the shock to
the driver.
LOCATION OF COMPONENTS
AB±24SRS AIRBAG ± Troubleshooting
WhereEverybodyKnowsYourName

CHECK TERMINAL TT OUTPUT
VOLTAGE
AT00R±01
When a voltmeter is connected to the DLC1, the following
items can be checked.
1. Throttle position sensor signal
2. Brake signal
3. Shift position signal
1. VOLTMETER CONNECTION Connect the positive (+) probe of the voltmeter to terminal T
T
and the negative (±) probe to terminal E1 of the DLC2.
HINT: If a voltmeter with small internal resistance is used, the
correct voltage will not be indicated, so use a voltmeter with
an internal resistance of at least 10 k
.
2. TURN IGNITION SWITCH TO ON (DO NOT START THE
ENGINE)
3. CHECK THROTTLE POSITION SENSOR SIGNAL Check if the voltage changes from approximately 0 V to
approximately 8 V when the accelerator pedal is gradually
depressed from the fully closed position.
4. CHECK BRAKE SIGNAL (LOCK±UP CUT SIGNAL)
(a) Open the throttle valve fully to apply approximately 8 V to terminal T
T.
(b) In this condition, check terminal T
T voltage when the brake
pedal is depressed and released.
TT terminal voltage:
0 V (When brake pedal is depressed)
8 V (When brake pedal is released)
5. START ENGINE
6. CHECK SHIFT POSITION SIGNAL (VEHICLE SPEED ABOVE 60 KM/H OR 37 MPH)
Check up±shifting together with terminal T
T voltage.
HINT: Check for light shocks from up±shifting and for
changes in the tachometer.
 Gear Position Terminal TT output voltage 1st GearBelow 0.5 V 

2nd Gear1.5 ~
2 6 V
 3rd Gear3.5 ~ 4.6 V
 3rd Lock±up4.5 ~ 5.9 V
 O/D5.5 ~ 6.9 V
 O/D Lock±up6.5 ~ 7.9 V
If terminal TT output voltage check cannot be performed, per-
form the check of terminal T
T circuit on page AT±120.
±
A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTINGAT±39
WhereEverybodyKnowsYourName