1991 LEXUS SC400 sensor

1
NG
OK
(1) Turn ignition switch LOCK, and wait at least 20
seconds.
(2) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(3) Repeat operation in step (1) and (2) at least 5 times.
(4) Using SST, connect terminals Tc and E
1 of TDCL.
SST 09843±18020
(5) Check diagnostic code.
Is diagnostic code 31 output again?
Using simulation method, reproduce
malfunction symptoms (See page IN±20).
Clear malfunction code stored in memory
(See page
AB±32).
Replace center airbag sensor assembly.
INSPECTION PROCEDURE
HINT:When a malfunction code other than code 31 is displayed at the same time, fi\
rst repair the malfunction indicated by the malfunction code other than code 31.
±
SRS AIRBAG TroubleshootingAB±81
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OK
Check operation of airbag warning light.
NG1
WIRING DIAGRAM
2Is diagnostic code 41 output again? System is normal.
Check harness between ECU±B
fuse and center airbag sensor as-
sembly. If normal, replace center
airbag sensor assembly.
Perform troubleshooting according to
malfunction code output. NO
YES
Diag. Code 41Malfunction Stored in Memory
CIRCUIT DESCRIPTION
If a malfunction occurs in the airbag system, malfunction codes 11 to 31 may be output, and when the
battery is disconnected after the malfunction is repaired, malfunction codes 11 to 31 will be cleared,
but code 41 will be output instead.
So long as the cancellation operation for a malfunction stored in memory (\
See page
AB±32) is not per-
formed, code 41 is stored in the center airbag sensor assembly and the airbag w\
arning light remains
lit up.
Code No.Diagnosis
41
Malfunction recorded in memory.41
Center airbag sensor assembly malfunction.
DIAGNOSTIC CHART
AB±82±
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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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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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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.
±
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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