ignition LEXUS SC300 1991 Service Workshop 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
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
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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
SRS 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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(1) Turn ignition switch LOCK.
(2) Disconnect center airbag sensor assemblyconnector.
(3) Turn ignition switch ON. But do not start engine.
(4) Measure voltage at IG
2 or ACC on connector
wire harness side of center airbag assembly and
operate electric system (defogger, wiper,
headlight, heater, blower, etc.).
Voltage: 6 V ± 11.5 V at IG
2 and ACC.
(5) Turn electric system switch OFF.
(6) Turn ignition switch LOCK.
(7) Remove voltmeter and connect center airbag sensor assembly.
Does airbag warning light turn off after approx. 10 seconds?
Preparation.
Turn ignition switch ON.
Operate electric system checked in [ 1 ] (4) and
check that airbag warning light goes off after
approx. 10 seconds.
Check diagnostic code, and if a malfunction
code is output, perform troubleshooting
according to malfunction code. If a normal
code is output, replace center airbag
sensor assembly.
Check battery and charging system
(See page CH±1)
INSPECTION PROCEDURE
AB±41SRS AIRBAG ± Troubleshooting
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(1) Connect connector to center airbag sensorassembly.
(2) Using a service wire, connect D
+, D± on spiral
cable side of connector between spiral cable
and steering wheel pad.
(3) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
Check squib circuit.
Codes other than code 11 may be output at this
time, but this is not relevant.
Measure resistance between D+, D± on spiral cable
side of connector between spiral cable and steer-
ing wheel pad and body ground.
Go to step [ 8 ].
Diagnostic code 11 is not output.
Resistance: 1 M
or higher
Replace center airbag sensor assembly.
Check center airbag sensor assembly.
(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. AB±45
SRS AIRBAG
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(1) Turn ignition switch LOCK.
(2) Disconnect battery negative (±) terminal cable,and wait at least 20 seconds.
(3) Connect steering wheel pad (squib) connector.
(4) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
Check squib.
Disconnect front airbag sensor connector.
Measure resistance between each terminal of
front airbag sensor.
Replace front airbag sensor.
Diagnostic code 11 is not output.
Replace steering wheel pad.
wDo not touch ohmmeter probes strongly against
terminals of front airbag sensor.
w Make sure the front airbag sensor connector is
properly connected.
From the results of the above inspection, the malfunctioning part can now be\
considered normal.
To make sure of this, use the simulation method to check.
Repair or replace harness or connector between center airbag sensor assembly a\
nd front airbag
sensor (See page AB±20).
Check front airbag sensor.
(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.
Codes other than code 11 may be output at this
time, but this is not relevant.
AB±46
SRS AIRBAG
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(1) Disconnect battery negative (±) terminal cable,and wait at least 20 seconds.
(2) Remove steering wheel pad (See page AB±14).
Check front airbag sensor circuit. (Measure resistance between terminals +SR\
and
±SR, +SL and ±SL of center airbag sensor assembly connector.
Preparation.
Disconnect center airbag sensor assembly con-
nector.
Measure resistance between terminals +SR and
±SR, +SL and ±SL of harness side connector of
center airbag sensor assembly.
Go to Code 15 (See page AB±68).
When storing steering wheel pad, keep upper
surface of the pad facing upward.
Resistance: 755
± 855

Check front airbag sensor circuit. (Measure voltage between terminal +S\
R or +SL
of center airbag sensor assembly connector and body ground.
(1) Connect negative (±) terminal cable to
battery.
(2) Turn ignition switch ON.
Repair or replace harness or connector
between center airbag sensor assembly
and front airbag sensor (See page AB±20).
Resistance: 1 V
Measure voltage between terminals +SR or +SL
of harness side connector of center airbag sensor
assembly and body ground.
INSPECTION PROCEDURE
AB±50SRS AIRBAG ± Troubleshooting
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(1) Turn ignition switch LOCK.
(2) Disconnect negative (±) terminal cable frombattery.
(3) Connect connector to center airbag sensor assembly.
(4) Using a service wire, Connect D
+ and D± on
spiral cable side of connector between spiral
cable and steering wheel pad.
(5) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
Check squib circuit.
Codes other than code 12 may be output at this
time, but this is not relevant.
Measure voltage at D+ on spiral cable side of con-
nector between spiral cable and steering wheel
pad.
Go to step [ 7 ].
Resistance: 1 V
Replace center airbag sensor assembly.
Check center airbag sensor assembly.
(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.
Diagnostic code 12 is not output. AB±51
SRS AIRBAG
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(1) Turn ignition switch LOCK.
(2) Disconnect battery negative (±) terminal cable,and wait at least 20 seconds.
(3) Connect steering wheel pad (squib) connector.
(4) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
Check squib.
Measure voltage at D+ on spiral cable side of con-
nector between spiral cable and steering wheel
pad.
Repair or replace spiral cable.
Diagnostic code 12 is not output.
Replace steering wheel pad.
From the results of the above inspection, the malfunctioning part can now be\
considered normal.
To make sure of this, use the simulation method to check.
Repair or replace harness or connector between center airbag sensor assembly a\
nd spiral cable.
Check spiral cable.
(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.
Codes other than code 12 may be output at this
time, but this is not relevant.
Voltage: Below 1 V
(1) Turn ignition switch LOCK.
(2) Disconnect connector between center airbag sensor assembly and spiral cable.
(3) Turn ignition switch ON.
AB±52
SRS AIRBAG
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