1991 LEXUS SC300 clock reset

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
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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
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Steering Wheel Pad (Airbag and Inflator)
Junction Block No. 1 Center Airbag
Front Airbag Sensor
Front Airbag Sensor
Warning Light Spiral Cable (in Combination Switch)
HANDLING PRECAUTIONS ON RELATED COMPONENTS
1. SRS AIRBAG
Locations of Airbag Components
This vehicle has an SRS AIRBAG (referred to as the airbag in the remain\
der of this manual).
When handling airbag components (removal, installation or inspection, e\
tc.), always follow the directions
given in the repair manual for the relevant model year to prevent the oc\
currence of accidents and airbag
malfunction.
Also take the following precautions when repairing the body:

Work must be started after 20 seconds or longer from the time the ignitio\
n switch is set to the LOCK
position and the negative (-) terminal cable is disconnected from the \
battery.
(The airbag system is equipped with a back-up power source so that if w\
ork is started 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
systems will be cancelled. So before starting work, make a record of the\
contents memorized by each
memory system. Then when work is finished, reset the clock and audio sys\
tems as before.
When the vehicle has tilt and telescopic steering, power seat, and outsi\
de rear view mirror, which are all
equipped with memory function, it is not possible to make a record of th\
e memory contents.
So when the operation is finished, it will be necessary to explain this \
fact to the customer, and request
the customer to adjust the features and reset the memory.
To avoid erasing the memory of each memory system, never use back-up powe\
r supply from outside
the vehicle.

When using electric welding, first disconnect the airbag connector (yel\
low color and 2 pins) under the
steering column near the combination switch connector before starting wo\
rk.
Sensor Assembly
INTRODUCTIONIN-6
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Fuel Pump ECUAuto Antenna Motor and Relay
Power Seat ECU
(For Passenger's Seat)
Power Seat ECU
(For Driver's Seat) CD Automatic Changer
Wireless Door Lock ECU
Moon Roof Control Relay
Locations of ECUs (Cont'd)
Many ECUs are mounted in this vehicle.
Take the following precautions during body repair to prevent damage to th\
e ECUs.


Before starting electric welding operations, disconnect the negative (-\
) terminal cable from the battery.
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\
contents memorized by each
memory system. Then when work is finished, reset the clock and audio sys\
tems as before.
When the vehicle has tilt and telescopic steering, power seat and outsid\
e rear view mirror, which are all
equipped with memory function, it is not possible to make a record of th\
e memory contents.
So when the operation is finished, it will be necessary to explain this \
fact to the customer, and request
the customer to adjust the features and reset the memory.

Do not expose the ECUs to ambient temperatures above 80 °C (176 °F).
NOTICE: If it is possible the ambient temperature may reach 80°C (176°F) or, more, remove the ECUs
from the vehicle before starting work.

Be careful not to drop the ECUs and not to apply physical shocks to them\
.
5. COMPONENTS ADJACENT TO THE BODY PANELS
Various types of component parts are mounted directly on or adjacently to\
the body panels.
Strictly observe the following precautions to prevent damaging these com\
ponents and the body panels
during handling.

Before repairing the body panels, remove their adjacent components or ap\
ply protective covers over
the components.

Before prying components off using a screwdriver or a scraper, etc., attach protective tape to the tool
tip or blade to prevent damaging the components and the body paint.

Before removing components from the outer surface of the body, attach protective tape to the body to
ensure no damage to painted areas.
HINT: Apply touch-up paint to any damaged paint surfaces.

Before drilling or cutting sections, make sure that there are no wires, \
hoses, etc., on the reverse side.
INTRODUCTIONIN-9
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GENERAL DESCRIPTION
The LEXUS SC400/300 is equipped with an SRS (Supplemental Restraint System\
) such as the driver
airbag and front passenger airbag. Failure to carry out service operations in \
the correct sequence
could cause the SRS to unexpectedly deployed during servicing, possibly leadin\
g to a serious acci-
dent. Further, if a mistake is made in servicing the supplemental restraint system, i\
t is possible the
SRS may fail to operate when required. Before performing servicing (inc\
luding removal or installa-
tion of parts, inspection or replacement), be sure to read the followin\
g items carefully, then follow
the correct procedure described in the repair manual.
1. Malfunction symptoms of the supplemental restraint system are difficult to confirm, so the diagnostic trouble codes become the most important source of information when troubleshooting. When
troubleshooting the supplemental restraint system, always inspect the diagnostic trouble codes before
disconnecting the battery (See page RS±59).
2. Work must be started after 90 seconds from the time the ignition switch turn\
ed to the LOCK position
and the negative (±) terminal cable is disconnected from the battery. (The supplemental restraint
system is equipped with a back±up power source so that if work is sta\
rted within 90 seconds of
disconnecting the negative (±) terminal cable of the battery, the SRS may be deployed.)
When the negative (±) terminal cable is disconnected from the battery, memory of the clock and audio sys-
tems will be canceled. So before starting work, make a record of the contents memo\
rized by the audio
memory system. When work is finished, reset the audio systems as before and ad\
just 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 custom-
er, 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 SRS does not deploy, the steering wheel pad, front passenger
airbag assembly, front airbag sensors and center airbag sensor assembly should be inspe\
cted (See pages
RS±16 , 28 , 41 and 44).
4. Never use SRS parts from another vehicle. When replacing parts, replace \
them with new parts.
5. Before repairs, remove the airbag sensor if shocks are likely to be applied to the sensors during r\
epairs.
6. Never disassemble and repair the steering wheel pad, front passenger airbag a\
ssembly, front airbag sensors or center airbag sensor assembly in order to reuse it.
7. If the steering wheel pad, front passenger airbag assembly, front airbag sensors or center airbag sensor assembly have been dropped, or if there are cracks, dents or dents or ot\
her defects in the case, bracket
or connector, replace them with new ones.
8. Do not expose the steering wheel pad, front passenger airbag assembly, front airbag sensors and center airbag sensor assembly directly to hot air or flames.
9. Use a volt/ohmmeter with high impedance (10 k
/V minimum) of troubleshooting of the system's electrical
circuit.
10. Information labels are attached to the periphery of the SRS components. \
Follow the instructions on the
notices.
11. After work on the supplemental restraint system is completed, perform the SRS\
warning light check (See page RS±59 ).
12. If the vehicle is equipped with a mobile communication system, refer to \
the precaution in the IN section. RS±2
±
SUPPLEMENTAL RESTRAINT SYSTEM GENERAL DESCRIPTION
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177
SRS AIRBAG
NOTICE: When inspecting or repairing the SRS AIRBAG, perform the operation in accord\
ance with the
following precautionary instructions and the procedure and precautions in the Repair Manual for the applicable
model year.

Malfunction symptoms of the airbag system are difficult to confirm, so the diagnostic codes become the most
important source of information when troubleshooting.
When troubleshooting the airbag system, always inspect the diagnostic codes before disconnecting the
battery.

Work must be started after 30 seconds or longer from the time the Ignition SW is set to the ªLOCKº position
and the negative (±) terminal cable is disconnected from the battery.
(The airbag system is equipped with a back±up power source so that if work is started within 30 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 systems
will be cancelled. So before starting work, make a record of the contents memorized by each me\
mory system.
Then when work is finished, reset the clock and audio system as before.
When the vehicle has tilt and telescopic steering, power seat, outside r\
ear 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
request 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.

When removing the steering wheel pad or handling a new steering wheel pad, keep the pad upper surfa\
ce
facing upward. Also, lock the lock lever of the twin lock type connector\
at the rear of the pad and take care
not to damage the connector.
(Storing the pad with its metallic surface up may lead to a serious accident if \
the airbag inflates for some
reason).

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

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

Never disassemble or repair the steering wheel pad, center airbag sensor asse\
mbly or front airbag sensors.

Before repairing the body, remove the airbag sensors if during repair shocks are likely to be app\
lied to the
sensors due to vibration of the body or direct tapping with tools or oth\
er parts.

Do not reuse a steering wheel pad or front airbag sensors.
After evaluating whether the center airbag sensor assembly is damaged or not, decide whether or not to reuse
it. (See the Repair Manual for the method for evaluating the center airbag\
sensor assembly.)

When troubleshooting the airbag system, use a high±impedance (Min. 1\
0k W/V) tester.

The vehicle wiring harness exclusively for the airbag system is distinguish\
ed by corrugated yellow tubing, as
are the connectors.

Do not measure the resistance of the airbag squib.
(It is possible this will deploy the airbag and is very dangerous.)

If the wire harness used in the airbag system is damaged, replace the wh\
ole wire harness assembly.
When the connector to the airbag front sensors can be repaired alone (when \
there is no damage to the wire
harness), use the repair wire specially designed for the purpose.
(Refer to the Repair Manual for the applicable Model year for details o\
f the replacement method.)

INFORMATION LABELS (NOTICES) are attached to the periphery of the airbag componen\
ts. Follow the
instructions on the notices.
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