LEXUS SC400 1991 Service Repair Manual

NGOK
NGOK
INSPECTION PROCEDURE
HINT: If the diagnostic trouble code is not displayed, perform the following \
troubleshooting:
1Check voltage between terminals Tc and E1 of DLC1 or DLC2.
C
OK
PTurn ignition switch ACC or ON.
Measure voltage between terminals Tc and E
1 of DLC1
or DLC2.
Voltage: Battery positive voltage
Go to step
.
2Check voltage between terminal Tc of DLC1 or DLC2 and body ground.
C
OK
Measure voltage between terminal Tc of DLC1 or DLC2
and body ground.
Voltage: Battery positive voltage
Check harness between terminal E1 of DLC1 or DLC2
and body ground.
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SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±123
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3Check center airbag sensor assembly.
C
OK
P1. Turn ignition switch LOCK.
2. Disconnect battery negative (±) terminal cable, andwait at least 90 seconds.
3. Remove steering wheel pad (See page RS±19).
4. Disconnect connectors of front passenger airbag assembly (See page RS±32).
Check operation of SRS warning light.
SRS warning light comes on.
Check harness between center airbag sensor assembly
and DLC1 or DLC2.
Replace center airbag sensor assembly.
RS±124±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
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HINT: If the diagnostic trouble code is continuously displayed, perform the f\
ollowing troubleshooting.
1Check resistance between terminal Tc of center airbag sensor assembly and body ground.
C
OK
P1. Turn ignition switch LOCK.
2. Disconnect center airbag sensor assembly con-nector.
3. Disconnect battery negative (±) terminal cable, and wait at least 90 seconds.
4. Remove steering wheel pad (See page RS±19).
5. Disconnect connectors of front passenger airbag assembly (See page RS±32).
Check resistance between terminal Tc of center airbag
sensor assembly and body ground.
Resistance: 1 M
or higher
Replace center airbag sensor assembly.
Repair or replace harness or connector.
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SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±125
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SERVICE SPECIFICATIONS
SERVICE DATA
RS02S±01
\
\
FRONT AIRBAG SENSOR\
 \

\
\

S ±
A\
 \
755±855

\
\

S ± S\
 \
1 M
or Higher
\
\
 S ± A\
 \
Less than 1

TORQUE SPECIFICATIONS
RS02T±07
\
\
Part tightened NVm kgf Vcm ft Vlbf
\
\
Steering wheel 35 360 26
\
\
Steering wheel pad 7.4 75 65 in. Vlbf
\
\
Front passenger airbag assembly 21 210 15
\
\
Front airbag sensor 25 260 19
\
\
Center airbag sensor assembly 15 150 11
RS±126±
SUPPLEMENTAL RESTRAINT SYSTEM SERVICE SPECIFICATIONS
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SUPPLEMENTAL RESTRAINT SYSTEM
RS±1
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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
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SUPPLEMENTAL RESTRAINT SYSTEM GENERAL DESCRIPTION
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STEERING WHEEL PAD (with AIRBAG)
RS00Q±07
1. When removing the steering wheel pad or handling a new steering wheel pad, it should be placedwith 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 steer\
ing wheel pad on top of another
one. (Storing the pad with its metallic surface up may lead to a serious ac\
cident if the airbag inflates for
some reason.
2. Never measure the resistance of the airbag squib. (This may cause the airbag\
to deploy, which isvery dangerous.)
3. Grease should not be applied to the steering wheel pad and the pad should not \
be cleaned withdetergents of any kind.
4. Store the steering wheel pad where the ambient temperature below 93
C (200
F), without high
humidity and away from electrical noise.
5. When using electric welding, first disconnect the SRS connector (yellow\
color and 2 pins) under the steering column near the combination switch connector before startin\
g 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 RS±21).
Perform the operation in a place away from electrical noise.
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SUPPLEMENTAL RESTRAINT SYSTEM GENERAL DESCRIPTIONRS±3
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SPIRAL CABLE (in COMBINATION SWITCH)
RS00P±06
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 page RS±19 of this manual concerning correct steering wheel installation.
FRONT PASSENGER AIRBAG ASSEMBLY
RS00N±07
1. Always store a removed or new front passenger airbag assembly with the a\
irbag door facing up.
Store the airbag assembly with the airbag door facing down could cause a seri\
ous accident if the
airbag inflates.
2. Never measure the resistance of the airbag squib. (This may cause the airbag\
to deploy, which isvery dangerous.)
3. Grease should not be applied to the front passenger airbag assembly and \
the door should not be
cleaned with detergents of any kind.
4. Store the front passenger airbag assembly where the ambient temperature remai\
ns below 93
C
(200
F), without high humidity and away from electrical noise.
5. When using electric welding, first disconnect the SRS connector (yellow col\
or and 2 pins) installed
on the glove compartment door finish plate at upper side of the glove co\
mpartment assembly
before starting work.
6. When disposing of a vehicle or the front passenger airbag assembly alone\
, the airbag should be deployed using an SST before disposal (See page RS±34). Perform the operation in a place away
from electrical noise.
RS±4
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SUPPLEMENTAL RESTRAINT SYSTEM GENERAL DESCRIPTION
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FRONT AIRBAG SENSOR
RS00N±07
1. Never reuse the front airbag sensor involved in a collision when the airbag h\
as deployed. (Replace boththe left and right airbag sensors.)
2. Install the front airbag sensor with the arrow on the sensor facing towa\
rd 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 sensors is equipped with an electrical connection check me\
chanism. Be sure 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 RS±12).
CENTER AIRBAG SENSOR ASSEMBLY
RSOOR±0A
1. Never reuse the center airbag sensor assembly involved in a collision when the airbag has
deployed.
2. Work must be started after 90 seconds from the time the ignition switch is t\
urned to LOCK position and the negative (±) terminal cable is disconnected from the batter\
y even just loosing the set bolts
of center airbag sensor assembly.
WIRE HARNESS AND CONNECTOR
RSO41±01
The SRS wire harness is integrated with the cowl wire harness assembly. The wires for the SRS wire har-
ness are encased in a yellow corrugated tube. All the connectors for the sys\
tem are also a standard yellow
color. If the SRS wire harness becomes disconnected or the connector becomes broken du\
e to an accident
etc., repair or replace it as shown on page RS±48.
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SUPPLEMENTAL RESTRAINT SYSTEM GENERAL DESCRIPTIONRS±5
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DESCRIPTION
RS00S±02
The SRS (Supplemental Restraint System), together with the seat belt, is designed to help protect the driv-
er. Frontal inspect, the airbag sensor detect the shock, and if the front±\
to±rear shock is greater than a spe-
cified value, an airbag stored in the steering wheel pad is inflated ins\
tantaneously to help reduce the shock
to the driver.
LOCATION OF COMPONENTS
RS00T±02
RS±6±
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