LEXUS SC400 1991 Service Repair Manual

1
(1) Turn ignition switch LOCK.
(2) Disconnect negative (±) terminal cable frombattery.
(3) Disconnect center airbag sensor assembly connector.
(4) Connect negative (±) terminal cable to battery.
Does airbag warning light turn off?
Check airbag warning light circuit or terminal
AB circuit of TDCL or check connector.NG
YES
Check operation of airbag warning light.
Replace center airbag sensor assembly.
INSPECTION PROCEDURE
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SRS AIRBAG TroubleshootingAB±85
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NG
Check voltage between terminals Tc and E
1of TDCL or check connector.
OK1
2
3
1
NG
NG
NG OK
OK
OK
3
Check voltage between terminal Tc of TDCL
or check connector and body ground.Check center airbag sensor assembly.
Replace center airbag sensor assemly.
Check resistance between terminal Tc of
center airbag sensor assembly and body
ground.
HINT: If the diagnostic code is continuously displayed, perform the following \
troubleshooting:
Repair or replace harnes or connector. Replace center airbag sensor
assembly.
Check harness between center
airbag sensor assembly and
TDCL or check connector.
Check harness between terminal
E1 of TDCL or check connector
and body ground.
Go to step
Tc Terminal Circuit
CIRCUIT DESCRIPTION
By connecting terminals Tc and E of the TDCL or check connector, the center airbag sensor assembly
is set in the diagnostic code output mode. The diagnostic codes are disp\
layed by the blinking of the
airbag warning light.
DIAGNOSTIC CHART
Troubleshooting
for this system is dif ferent depending on whether the diagnostic code is not displayed
or is continuously displayed. Confirm the problem symptoms first before se\
lecting the appropriate
troubleshooting procedure.
HINT: If the diagnostic code is not displayed, perform the following trouble\
shooting:
AB±86
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WIRING DIAGRAM
DIAGNOSTIC CHART
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SRS AIRBAG TroubleshootingAB±87
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INSPECTION PROCEDURE
HINT: If the diagnostic code is not displayed, perform the following troubles\
hooting:
Check voltage between terminals Tc and E1 of TDCL or check connector.
nector
Turn ignition switch ACC or ON. Measure voltage between terminals Tc and E
1 of
TDCL or check connector.
Voltage: 10 ± 14 V
Measure voltage between terminal Tc of TDCL or
check connector and body ground.Voltage: 10 ± 14 V
Check harness between terminal E1 of TDCL
or check connector and body ground
Check voltage between terminals Tc or TDCL or check connector and
body ground.
AB±88±
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NGOK
Check center airbag sensor assembly.3
(1) Disconnect negative (±) terminal cable from
battery, and wait at least 20 seconds.
(2) Turn ignition switch lock.
(3) Disconnect center airbag sensor assembly
connector.
(4) Using a service wire, connector terminal Tc of center airbag sensor assembly connector to
body ground.
(5) Install the center airbag sensor assembly.
(6) Connect negative (±) terminal cable to battery.
(7) Turn ignition switch ACC or ON.
Check operation of airbag warning light.
Airbag light comes on.
Check harness between center airbag sensor
assembly and TDCL or check connector.
Replace center airbag sensor assembly.
C
P
OK
CautionNever turn ignition switch ACC or ON and
never connect negative (±) terminal to battery
before the center airbag sensor assembly is
installed.
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SRS AIRBAG TroubleshootingAB±89
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NGOK
Check resistance between terminal Tc of center airbag sensor
assembly and body ground.1
Check resistance between terminal Tc of center
airbag sensor assembly and body ground.
Replace center airbag sensor assembly.
Resistance: 1M

or higher
(1) Turn ignition switch LOCK.
(2) Disconnect center airbag sensor assembly
connector.
Repair or replace harness or connector.
HINT: If the diagnostic code is continuously displayed, perform the followin\
g troubleshooting. AB±90
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DISPOSAL OF STEERING WHEEL
PAD (WITH AIRBAG)
When scrapping vehicles equipped with an airbag system or dis-
posing of a steering wheel pad (with airbag), always first deploy
the airbag in accordance with the procedure described below.
If any abnormality occurs with the airbag deployment, contact the
SERVICE DEPT. of TOYOTA MOTOR SALES, U.S.A., INC..
Never dispose of a steering wheel pad which has an
undeployed airbag.
When disposing of a steering wheel pad with an airbag deployed
in a collision, follow the same procedure given under ªAIRBAG
DEPLOYMENT PROCEDURE (WHEN SCRAPPING THE VE-
HICLE), part 5, DISPOSAL OF STEERING WHEEL PAD (WITH
AIRBAG)º (See page AB±93).
PRECAUTIONS FOR AIRBAG DEPLOYMENT
1. 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.
2. 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.
3. When deploying an airbag, perform the operation from at least 10 m (33 ft) away from the steering wheel pad.
4. The steering wheel pad is very hot when the airbag is deployed, so leave it alone for at least 30 minutes after
deployment.
5. Use gloves and safety glasses when handling a steering
wheel pad with deployed airbag.
6. Always wash your hands with water after completing the operation.
7. Do not apply water, etc. to a steering wheel pad with deployed airbag.
AIRBAG DEPLOYMENT PROCEDURE
(WHEN SCRAPPING VEHICLE)
HINT: Have a battery ready as the power source to deploy the
airbag.
1. DISCONNECT NEGATIVE (±) TERMINAL CABLE FROM BATTERY
CAUTION: Work must be started after approx. 30 sec-
onds or lo nger from the time the ignition switch is turned
to the LOCK position and the negative (±) terminal cable
is disconnected from the battery (See page AB±2).
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SRS AIRBAG Disposal of Steering Wheel Pad (with Airbag)AB±91
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2. CONFIRM FUNCTIONING OF SST (See page AB±97)
SST 09082±00700
3. INSTALL SST CAUTION: Check that there is no looseness in the
steering wheel and steering wheel pad.
(a) Remove the No. 1 under cover.
(b) Disconnect the airbag connector of the spiral cable.
(c) Connect the SST connector to the airbag connector ofthe spiral cable.
SST 09082±00700
(d) Move the SST to at least 10 m (33 ft) from the front of the
vehicle.
(e) Close all the doors and windows of the vehicle.
NOTICE: Take care not to damage the SST wire harness.
(f) Connect the SST red clip to the battery positive (+) terminal and the black clip to the battery negative (±)
terminal.
4. DEPLOY AIRBAG (a) Confirm that no±one is inside the vehicle or within 10 (33 ft) of the vehicle.
(b) Press the SST activation switch and deploy the airbag.
HINT: The airbag deploys simultaneously as the LED of the
SST activation switch lights up.
AB±92
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5. DISPOSAL OF STEERING WHEEL PAD (WITH AIRBAG)CAUTION:
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 Do not apply water, etc. to a steering wheel pad with
deployed airbag.
w Always wash your hands with water after completing the
operation.
(a) When scrapping a vehicle, deploy the airbag and scrap
the vehicle with the steering wheel pad still installed.
(b) When moving a vehicle for scr apping which has a
steering wheel pad with deployed airbag, use gloves
and safety glasses.
AIRBAG DEPLOYMENT PROCEDURE
(PROCEDURE FOR DISPOSAL OF
STEERING WHEEL PAD ONLY)
When disposing of the steering wheel pad (with airbag)
only, never use the customer's vehicle to deploy the
airbag.
Remove the steering wheel pad from the vehicle and be sure
to follow the procedure given below when deploying the
airbag.
HINT: Have a battery ready as the power source to deploy the
airbag.
1. REMOVE STEERING WHEEL PAD (SEE PAGE AB±16)
CAUTION:
wWhen removing the steering wheel pad (with
airbag), work must be started after approx. 30
seconds or longer from the time the ignition switch
is turned to the LOCK position and the negative (±)
terminal cable is disconnected from the battery.
w When storing the steering wheel pad, keep the upper
surface of the pad facing upward.
2. REMOVE STEERING WHEEL PAD CONNECTOR
Remove the connector on the steering wheel pad rear
surface from the inflater cover.
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SRS AIRBAG Disposal of Steering Wheel Pad (with Aribag)AB±93
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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
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