1991 LEXUS SC400 airbag off

Diag. Code 22Airbag Warning Light System Malfunction
CIRCUIT DESCRIPTION
The airbag warning light is located on the combination meter.
When the airbag system is normal, the airbag warning light lights up for\
approx. 6 seconds after the
ignition switch is turned from LOCK position to ACC or ON position, and then turns off automatically.
If there is a malfunction in the airbag system, the airbag warning light\
lights up to inform the driver of
the abnormality.
When terminals Tc and E of the TDCL are connected, the diagnostic code is displayed by t\
he blinking
of the airbag warning light.
The airbag warning light circuit is equipped with an electrical connecti\
on check mechanism which
detects when the connector to the center airbag sensor assembly is not p\
roperly connected.
If the connector to the center airbag sensor assembly is not properly co\
nnected, the airbag warning
light will not light up.
Diagnostic code 22 is recorded when a malfunction occurs in the airbag w\
arning light system.
If an OPEN malfunction occurs in the airbag warning light system, the ai\
rbag warning light does not
light up, so that until the malfunction is repaired, the diagnostic code\
s (including code 22) cannot be
confirmed.
Code No.Diagnosis
22
Open circuit in airbag warning light system.22
Center airbag sensor assembly malfunction.
AB±74±
SRS AIRBAG Troubleshooting
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Clear malfunction code 41 stored in memory
(See page AB±32).
Check operation of airbag warning light.
NG
OK
1
Airbag warning light turns off.
(1) Turn ignition switch LOCK, and wait at least
2 seconds.
(2) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(3) Check operation of airbag warning light.
System is normal.
2Is diagnostic code 41 output again?
(1) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(2) Using SST, connect terminals Tc and E
1 of TDCL.
SST 09843±18020
(3) Check diagnostic code.
Check harness between ECU±B fuse and center
airbag sensor assembly. If normal, replace
center airbag sensor assembly.
Perform troubleshooting according to malfunction code output.
NG
OK
INSPECTION PROCEDURE
±
SRS AIRBAG TroubleshootingAB±83
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YES
Does airbag warning light turn off?
NO
1
Replace center airbag sensor assembly. Check airbag warning light circuit
or terminal AB circuit of TDCL or
check connector.
WIRING DIAGRAM
Airbag Warning Light System (Always Lit Up)
CIRCUIT DESCRIPTION
The airbag warning light is located on the combination meter.
When the airbag system is normal, the airbag warning light lights up for\
approx. 6 seconds after the
ignition switch is turned from LOCK position to ACC or ON position, and then turns off automatically.
If there is a malfunction in the airbag system, the airbag warning light\
lights up to inform the driver of
the abnormality.
When terminals Tc and E of the TDCL are connected, the diagnostic code is displayed by t\
he blinking
of the airbag warning light.
DIAGNOSTIC CHART
AB±84±
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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
±
SRS AIRBAG TroubleshootingAB±85
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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
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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
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3. PROTECT JOINED SECTIONWrap silicon tape around the joins to protect them from water.
HINT:
wBefore starting the operation, thoroughly wipe dirt and
grease off the sections to be joined.
wIf the adhesive surfaces of two tapes come in contact
they will stick together and will not come apart, so do not
remove the backing film except when using the tape.
wDo not let oil and dust, etc. get on the tape surface.
(a) Ready about 100 mm (3.94 in.) of silicon tape (Part No.
08231±00045) and peel off the film.
(b) Stretch the silicon tape until its width is reduced by half.
(c) About 10 mm (0.39 in.) from the end of the pressure±contact sleeve, wrap the silicon tape around
the sleeve three or more times while stretching the tape.
(d) Wrap the remaining part of sleeve with half of the tape overlapping at each turn.
(e) Firmly wrap the tape two times or more about 10 mm (0.39 in.) from the other end of the pressure±contact
sleeve, then wrap the tape back towards the start again
and firmly finish winding the tape around the center of
the sleeve.
(f) Fix the corrugated tube to the cabtire cable using silicon tape.
(g) After applying the silicon tape, apply vinyl tape on the corrugated tube of repair wire side over to the
corrugated tube of vehicle wire harness side.
AB±22
SRS AIRBAG
± Replacement of Repair Wire for Front Airbag Sensor
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How To Proceed With Troubleshooting
Malfunction symptoms of the airbag system are difficult to confirm, so the diagnostic codes become the most
important source of information when troubleshooting. Perform troubleshooting of the airbag system in ac\
cor-
dance with the following procedure:
HINT: Do not disconnect the battery negative (±) terminal cable until st\
ep [ 3 ], Diagnostic Code Check and Re-
cording, has been completed.1. CUSTOMER PROBLEM ANALYSIS Using the CUSTOMER PROBLEM ANALYSIS CHECK SHEET (See page AB±29) for reference, ask the
customer in as much detail as possible about the problem.
2. WARNING LIGHT CHECK Check the airbag warning light. If the light remains on, a malfunction is sto\
red in the center airbag sensor,
assembly, so proceed to step [ 3 ]. If the airbag warning light is not on, a malf\
unction has occurred in the
airbag warning light circuit, so perform troubleshooting for code 22.
HINT: Code 22 is recorded when a malfunction occurs in the airbag warning li\
ght system.
If an open malfunction occurs in the airbag warning light system, the airb\
ag warning light does not light up,
so that until the malfunction is repaired, the diagnostic codes (includin\
g code 22) cannot be confirmed.
3. DIAGNOSTIC CODE CHECK AND RECORDING Check the diagnostic codes and make a note of any malfunction codes which are\
output. If a normal code
is output, an abnormality in the power source circuit may have occurred, so perform troubleshootin\
g for
source voltage in step [ 8 ].
If code 22 is output, skip steps [ 4 ] and [ 5 ] and proceed to step [ 7\
].
4. CLEARING OF MALFUNCTION CODE (EXCEPT CODE 41) Clear the malfunction code.
HINT: The malfunction code output in step [ 3 ] indicates that a malfunction \
has occurred in the circuit desig-
nated by the malfunction code, but does not indicate whether the malfunction \
is still occurring or whether
it was in the past.
Accordingly, it is necessary to find out the present condition of the malfunction oc\
currence by clearing the
malfunction code and performing the diagnostic code check again. If this\
operation is neglected and trou-
bleshooting is performed using only the malfunction code confirmed in step [ 3 ], isola\
ting the problem com-
ponent becomes difficult and invites mistaken diagnosis.
5. DIAGNOSTIC CODE CHECK AND RECORDING [ 6 ] SYMPTOM SIMULATION After repeating ignition switch ON±OFF operation (ON: wait 20 secs., OFF: wait 20 secs.) 5 times, check
the diagnostic codes. If any code other than code 41 is output, the malfunc\
tion is still occurring, so proceed
to step [ 7 ].
If code 41 only is output, the following three cases are possible:
w Intermittent trouble occurred previously, but it is now normal.
w The problem has been corrected, but clearing of code 41 has been forgott\
en.
w There is a malfunction in the circuit for code 41.
Focusing on the circuit of the malfunction code stored in step 3, use th\
e simulation method in step [ 6 ]
in order to simulate the malfunction. If the malfunction occurs, proceed t\
o step [ 7 ]; if not, proceed to step.
[ 12 ]. AB±25
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± Troubleshooting
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