LEXUS SC400 1991 Service Repair Manual

11. DIAGNOSTIC CODE CHECKAfter repeating ignition switch ON±OFF operation (ON: wait 20 secs., OFF: wait 20 secs.) 5 times, check
the diagnostic codes. If only code 41 is displayed, proceed to step [ 12 ]. If a code other than code 41 is
displayed, return to step [ 7 ] and troubleshoot the displayed malfuncti\
on code.
NOTICE: When connecting the battery after clearing the malfunction code,\
always do it with the ignition
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 positi\
on, or the ignition switch is turned
ACC or ON within 2 seconds of connecting the battery, it is possible that the diagnosis system will not oper-
ate normally.
12. CLEARING OF MALFUNCTION CODE 41 STORED IN MEMORY Clear malfunction code 41 stored in memory. This operation is not necessary only in case that the power
source voltage returns to normal.
13. CONFIRMATION TEST Check the warning light again and confirm that all the malfunctions have been\
repaired. If the warning light
indicates an abnormality, repeat the operation again from step [ 2 ]. If code 41 is output at st\
ep [ 3 ], skip
steps [ 4 ] and [ 5 ] and proceed to step [ 7 ]. AB±27
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± Troubleshooting
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Customer Problem Analysis
Diagnostic Code Check and Recording P. AB±30
P.
AB±29
Warning Light Check P. AB±30
Diagnostic Code Check and Recording P. AB±30
Clearing of Malfunction Code (Except Code 41) P. AB±32
Diagnostic Code Chart P. AB±34
Circuit Inspection P. AB±40
Identification of Problem
Repair
Vehicle Brought to Workshop
Symptom SimulationP. IN±20
Clearing of Malfunction Code (Except Code 41) P. AB±32
Diagnostic Code Check P. AB±30
Clearing of Malfunction Code 41 Stored in Memory P. AB±32
Confirmation Test
ENDOnly Code 41 Output
Output Other Than Code 41
Output Other Than Code 41
Only Code 41
Output
Output Other ThanCode 41 Only Code 41
Output
Does Not Light Up
Normal Code
Malfunction Code
AB±28SRS AIRBAG ± Troubleshooting
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Customer Problem Analysis Check Sheet
SRS AIRBAG System Check Sheet
Registration No.
Customer 's NameRegistration Year/ /
Frame No.
Date Vehicle
Brought In/ /Odometer ReadingKm
Miles
Date of Problem Occurrence / /
WeatherFine Cloudy Rainy Snowy Various/Other
Conditions
Outdoor
TemperatureHot Warm Cool Cold (Approx.
C (
F))
Conditions
at Time
of Problem
OccurrenceVehicle
Operation
 Starting Idling
 Driving
 Constant speed Acceleration Deceleration Other]
[
Condition
of road
Details of Problem
Vehicle Inspection,
Repair History Prior
to Occurrence of
Malfunction
(Including Airbag
System)
(Diagnosis System Inspection)
Airba
g Warning1st Time Remain On Sometimes Lights Up Does Not Light UpAirbag Warning
Light Inspection2nd TimeRemain On Sometimes Lights Up Does Not Light Up
Diagnostic Code1st TimeNormal Code Malfunction Code [Code. ]Diagnostic Code
Inspection2nd TimeNormal Code Malfunction Code [Code. ]
AB±29SRS AIRBAG ± Troubleshooting
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Name:
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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
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± 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
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CLEARING OF DIAGNOSTIC CODE
1. CLEARING OF MALFUNCTION CODE(EXCEPT CODE 41)
Remove the battery negative (±) terminal or ECU±B fuse for
10 seconds or more with the ignition switch OFF.
NOTICE: When connecting the battery after cancelling
the malfunction code, always do it with the ignition
switch in LOCK position. If the battery is connected with
the ignition switch in ACC or ON position, there are cases
when the diagnosis system does not operate normally.
HINT:
wCode 41 cannot be cleared by this method.
wThe lower the temperature, the longer the battery
negative (±) terminal must be left off.
wOther memory systems (clock, audio system) will also
be cancelled out (See page AB±2).
2. CLEARING OF MALFUNCTION CODE 41 STORED IN MEMORY
(a) Connect service wires to terminals Tc and AB of theTDCL.
(b) Turn the ignition switch ACC or ON and wait approx. 6 seconds.
(c) S ta rtin g with th e Tc te rmin a l, ap p ly bo d y gr ound
alternately to terminal Tc and terminal AB twice each in
cycles of 1.0 ± 0.5 seconds. Finally, keep applying body
ground to terminal Tc.
HINT: When alternating between body ground of terminals Tc
and AB release one from body ground while applying it to the
other terminal. The time interval in between must be within
the following conditions. If it is out of the conditions, code 41
will not be cleared.
(d) After several seconds, when the airbag warning light
starts to blink in a 64 msec. cycle, cancellation is
completed.
HINT: This method clears not only code No. 41, but also other
malfunction codes all at once.
Except when instructed by the troubleshooting procedure,
use this method only when the repair procedure is completed
(See page AB±25).
AB±32
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± 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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MEMOAB±35
SRS AIRBAG
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Location of Connectors
LOCATION OF CONNECTORS IN INSTRUMENT PANEL
AB±36SRS AIRBAG ± Troubleshooting
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