1991 LEXUS SC400 sensor

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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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
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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
SRS AIRBAG
± Troubleshooting
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NOTICE: When connecting the battery after clearing the malfunction code, always\
do it with the igni-
tion switch in LOCK position. When the battery has been reconnected, turn the ignition switch to
ACC or ON position after at least 2 seconds have elapsed.
If the battery is reconnected with the ignition switch in ACC or ON posi\
tion, or the ignition switch
is turned to ACC or ON within 2 seconds of connecting the battery, it is possible that the diagnosis
system will not operate normally.
HINT: Determine the malfunction in the airbag system in step [ 6 ] by whethe\
r or not a malfunction code
other than code 41 is output.
7. DIAGNOSTIC CODE CHART Proceed to the appropriate flow chart in step [ 8 ] in accordance with the malfunction code found in step
[ 5 ] or [ 6 ].
8. CIRCUIT INSPECTION [ 9 ] REPAIR Find out if the problem lies in a sensor, actuator or wire harness and connector, and repair the problem.
After the problem part is repaired, reinstall the disassembled parts. Do not \
start work until at least 20 se-
conds after the ignition switch is turned to the LOCK position and the negati\
ve (±) terminal cable is discon-
nected.
CAUTION: If incorrect procedure is used, a malfunction may occur in the system o\
r there is the dan-
ger that airbag may be accidentally activated during the repair operation. Carefully read the GEN-
ERAL DESCRIPTION (See page AB±2) and the cautions for each operation, and perform repairs in
the correct order using the correct methods.
HINT: The following illustration for the CIRCUIT INSPECTION shows each conne\
ctor for the circuit from
the center airbag sensor assembly to the steering wheel pad (squib).
10 CLEARING OF MALFUNCTION CODE (EXCEPT CODE 41) When all the malfunction codes found in steps [ 5 ] and [ 6 ] have been repa\
ired, clear the malfunction
codes.
AB±26
SRS AIRBAG
± Troubleshooting
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Diagnosis Inspection
AIRBAG WARNING LIGHT CHECK
(a) Turn the ignition switch to ACC or ON and check that theairbag warning light lights up.
(b) Check that the airbag warning light goes out after approx. 6 seconds.
HINT:
wWhen the ignition switch is at ACC or ON and the airbag
warning light remains on, the center airbag sensor
assembly has detected a malfunction code.
wIf, after approx. 6 seconds have elapsed, the airbag
warning light sometimes lights up or the airbag warning
light lights up even when the ignition switch is OFF, a
short in the airbag warning light circuit can be
considered likely. Proceed to Airbag warning light
system (always lit up) on page AB±84.
DIAGNOSTIC CODE CHECK
1. OUTPUT DIAGNOSTIC CODE
(a) Turn the ignition switch to ACC or ON position and waitapprox. 20 seconds.
(b) Using SST, connect terminals Tc and E
1 of the TDCL.
SST 09843±18020
NOTICE: Never make a mistake with the terminal connec-
tion position as this will cause a malfunction.
2. READ DIAGNOSTIC CODE Read the diagnostic code as indicated by the number of
times the airbag warning light blinks.
wNormal code indication
The light will blink 2 times per second.
wMalfunction code indication
In the event of a malfunction, the light will blink. The first
number of the code No. will equal the first digit of a
2±digit diagnostic code, and after a 1.5 second pause,
the 2nd number of the code No. will equal the 2nd digit.
If there are two or more codes, there will be a 2.5 second
pause between each.
After all the codes have been output, there will be a 4.0 se-
cond pause and they will all be repeated.
HINT:
wIn the event of a number of trouble codes, indication will
begin from the smaller numbered code to the larger.
wIf a diagnostic code is not output or is continuously
output, proceed to the TC terminal circuit inspection on
page AB±86 .
AB±30
SRS AIRBAG
± Troubleshooting
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DIAGNOSTIC CODES
CodeNo.Blink PatternDiagnosisTrouble AreaAIRBAG
Warning Light
(Nor

System normal±OFF
(Nor-
mal)
Source Voltage drop
Battery

Center airbag sensor assemblyON
11

Short in squib circuit
(to ground)

Front airbag sensor
malfunction

Flower sensor malfunction
Steering wheel pad (squib)

Front airbag sensor

Spiral cable

Center airbag sensor assembly

Wire harness
ON
12

Short in squib circuit
(to +B)
Steering wheel pad (squib)

Front airbag sensor

Spiral cable

Center airbag sensor assembly

Wire harness
ON
13

Short in squib circuit
(between D+ wire harness
and D± wire harness)

Steering wheel pad (squib)

Spiral cable

Center airbag sensor assembly

Wire harness
ON
14

Open in squib circuit
Steering wheel pad (squib)

Spiral cable

Center airbag sensor assembly

Wire harness
ON
15

Open in front airbag
sensor circuit
Front airbag sensor

Center airbag sensor assembly

Wire harness
ON
22

Airbag warning light
system malfunction
Airbag warning light

Center airbag sensor assembly

Wire harness
ON
31

Center airbag sensor
assembly malfunction

Center airbag sensor assemblyON
41

Malfunction stored in
memory

(Center airbag sensor assembly)ON
HINT:
w When the airbag warning light remains lit up and the diagnostic code in the n\
ormal code, this means a
source voltage drop.
This malfunction is not stored in memory by the center airbag sensor ass\
embly and if the power source
voltage returns to normal, after approx. 10 seconds the airbag warning l\
ight will automatically go out.
w Code 22 in recorded when a malfunction occurs in the airbag warning light sy\
stem. If an open malfunction
occurs in the airbag warning light system, the airbag warning light does not l\
ight up, so that until the
mal±function is repaired, the diagnostic codes (including code 22) cannot be confi\
rmed.
w When a malfunction occurs in the airbag system, malfunction codes 11 to 31 are output. After repairing
the malfunction indicated by malfunction codes 11 to 31, codes 11 to 31 are cleared from the memory, but
code 41 is output instead. Once the malfunction has been detected, the airba\
g warning light will remain
lit up until code 41 is cleared, even though the malfunction has been re\
paired.
w When 2 or more codes are indicated, the lowest numbered code will appear\
first.
w If a code not listed on the chart is displayed, then the center airbag s\
ensor assembly is faulty. AB±31
SRS AIRBAG
± Troubleshooting
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Wiring Diagram
CENTER AIRBAG SENSOR ASSEMBLY CONNECTOR
No.SymbolTerminal NameNo.SymbolTerminal Name
18E2Ground
2±SRRH Front Airbag Sensor (±)9LAAirbag Warning Light
3+SRRH Front Airbag Sensor (+)10D±Squib (±)
4+SLLH Front Airbag Sensor (+)11D+Squib (+)
5±SLLH Front Airbag Sensor (±)12TcDiagnosis
6+BBattery (ECU±B Fuse)13E1Ground
7IG2Power Source (IGN Fuse)14AccPower Source (CIG Fuse)
AL1Electrical Connection Check
MechanismBL2Electrical Connection Check
Mechanism
AB±33SRS AIRBAG ± Troubleshooting
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Diagnostic Code Matrix Chart
If a malfunction code is displayed during the diagnostic code check, check\
the circuit listed for that code in the
table below (Proceed to the page given for that circuit).
Code No.DiagnosisPage
(Normal)*1Source voltage dropAB±40
11Short in squib circuit or front airbag sensor circuit (to ground)AB±42
12Short in squib circuit or front airbag sensor circuit (to +B)AB±48
13Short in squib circuit (between D+ wire harness and D± wire harness)\
AB±54
14Open in squib circuitAB±62
15Open in front airbag sensor circuitAB±68
22*2Airbag warning light system malfunctionAB±74
31Center airbag sensor assembly malfunctionAB±80
41*3Malfunction stored in memoryAB±82
HINT:
*1 When the airbag warning light remains lit up and the diagnostic code is the normal code, this means asource voltage drop.
*2 Code 22 is recorded when a malfunction occurs in the airbag warning light sy\
stem. If an open malfunction occurs in the airbag warning light system, the airbag warning light does not light up, so that until the mal-
function is repaired, the diagnostic code (including code 22) cannot be confir\
med.
*3 When a malfunction occurs in the airbag system, malfunction codes 11 to 31 are output. After repairing the malfunction indicated by malfunction codes 11 to 31, codes 11 to 31 are cleared from the memory, but
code 41 is output instead. Once the malfunction has been detected, the airba\
g warning light will remain
lit up until code 41 is cleared, even though the malfunction has been re\
paired.
Problem Symptom Chart
Proceed with troubleshooting of each circuit in the table below.
Problem SymptomInspection ItemPage

With the ignition switch at ACC or ON, the airbag warning light
sometimes lights up after approx. 6 seconds have elapsed.

Airbag warning light lights up even when ignition switch is in the
LOCK position.
Airbag warning light system
(Always lit up)AB±84

Diagnostic code not displayed.

Diagnostic code continuously displayed.
Tc terminal circuitAB±86
AB±34SRS AIRBAG ± Troubleshooting
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