1991 LEXUS SC400 ignition

(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
± Troubleshooting
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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
± Troubleshooting
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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
± Troubleshooting
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(1) Connect negative (±) terminal cable to battery.
(2) Clear malfunction code 41 stored in memory(See page AB±32).
Check center airbag sensor assembly.
Replace center airbag sensor assembly.
(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) Using SST, connect terminals Tc and E
1 of
TDCL.
SST 09843±18020
(4) Check diagnostic code.
Codes other than code 13 may be output at this
time, but this is not relevant to this check.
Diagnostic code 13 is not output.
(1) Turn ignition switch LOCK.
(2) Disconnect battery negative (±) terminal cable, and wait at least 2 seconds.
(3) Connect steering wheel pad (squib) connector.
(4) Connect negative (±) terminal cable to battery.
(5) Clear malfunction code 41 stored in memory
(See page AB±32).
Check squib.
Replace steering wheel pad.
Codes other than code 13 may be output at this
time, but this is not relevant to this check.
Diagnostic code 13 is not output.
(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) Using SST, connect terminals Tc and E
1 of
TDCL.
SST 09843±18020
(4) Check diagnostic code.
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. AB±57
SRS AIRBAG
± Troubleshooting
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DIAGNOSIS SYSTEM
AT09R±07
The electronically controlled transmission system has built±
in self±diagnostic functions. If the malfunction occurs in the
system, the ECM stores the malfunction code in memory and
the O/D OFF (Overdrive OFF) indicator light blinks to inform
the driver. The diagnostic trouble code stored in memory can
be read out by the following procedure.
O/D OFF INDICATOR LIGHT INSPECTION
AT09S±07
1. Turn the ignition switch to ON.
2. Check if the O/D OFF indicator light lights up when the O/D main switch is pushed out to OFF and goes off when
the O/D main switch is pushed in to ON.
HINT:
wIf the O/D OFF indicator light does not light up or stay on
all the time, carry out the check for ªO/D OFF Indicator
Light Circuitº on page AT±112.
w If the O/D OFF indicator light blinks, a trouble code is
stored in the ECM memory.
DIAGNOSTIC TROUBLE CODE CHECK
AT0A3±07
1. Turn the ignition switch ON, but do not start the engine.
2. Push in the O/D main switch to ON.
HINT: Warning and diagnostic trouble codes can be r ead only
when the O/D main switch is ON. If it is OFF, the O/D OFF indi-
cator lights up continuously and will not blink.
3. Using SST, connect terminals TE1 and E1 of the DLC2 or
DLC1.
SST 09843±18020
±
A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTINGAT±37
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4. Read the diagnostic trouble code indicated by thenumber of times the O/D OFF indicator light blinks.
HINT: If the system is operating normally, the light will blink
2 times per second.
The malfunction code is indicated as shown in the illustration
at left (Diagnostic trouble code ª42º is shown as an example).
HINT: When 2 or more trouble codes are stored in memory,
the lower±numbered code is displayed first.
If no diagnostic trouble code is output, or if a diagnostic
trouble code is output even though no diagnostic trouble
code output operation is performed, check the TE1 terminal
circuit on page AT±118.
DIAGNOSTIC TROUBLE CODE CHECK
BY USING LEXUS HAND±HELD TESTER
AT0RD±01
1. Hook up the LEXUS hand±held tester to the DLC2.
2. Read the diagnostic trouble codes by following theprompts on the tester screen.
Please refer to the LEXUS hand±held tester operator's
manual for further details.
CANCELING DIAGNOSTIC TROUBLE
CODE
AT09T±07
After repair of the trouble area, the diagnostic trouble code
retained in the ECM memory must be canceled out by remov-
ing the EFI fuse for 10 seconds or more, with the ignition
switch off.
Check that the normal code is output after connecting the
fuse.
AT±38
±
A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTING
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CHECK TERMINAL TT OUTPUT
VOLTAGE
AT00R±01
When a voltmeter is connected to the DLC1, the following
items can be checked.
1. Throttle position sensor signal
2. Brake signal
3. Shift position signal
1. VOLTMETER CONNECTION Connect the positive (+) probe of the voltmeter to terminal T
T
and the negative (±) probe to terminal E1 of the DLC2.
HINT: If a voltmeter with small internal resistance is used, the
correct voltage will not be indicated, so use a voltmeter with
an internal resistance of at least 10 k
.
2. TURN IGNITION SWITCH TO ON (DO NOT START THE
ENGINE)
3. CHECK THROTTLE POSITION SENSOR SIGNAL Check if the voltage changes from approximately 0 V to
approximately 8 V when the accelerator pedal is gradually
depressed from the fully closed position.
4. CHECK BRAKE SIGNAL (LOCK±UP CUT SIGNAL)
(a) Open the throttle valve fully to apply approximately 8 V to terminal T
T.
(b) In this condition, check terminal T
T voltage when the brake
pedal is depressed and released.
TT terminal voltage:
0 V (When brake pedal is depressed)
8 V (When brake pedal is released)
5. START ENGINE
6. CHECK SHIFT POSITION SIGNAL (VEHICLE SPEED ABOVE 60 KM/H OR 37 MPH)
Check up±shifting together with terminal T
T voltage.
HINT: Check for light shocks from up±shifting and for
changes in the tachometer.
 Gear Position Terminal TT output voltage 1st GearBelow 0.5 V 

2nd Gear1.5 ~
2 6 V
 3rd Gear3.5 ~ 4.6 V
 3rd Lock±up4.5 ~ 5.9 V
 O/D5.5 ~ 6.9 V
 O/D Lock±up6.5 ~ 7.9 V
If terminal TT output voltage check cannot be performed, per-
form the check of terminal T
T circuit on page AT±120.
±
A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTINGAT±39
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