warning LEXUS SC400 1991 Service Owner's Manual

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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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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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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Circuit Inspection
Diag. Code (Normal)Source Voltage Drop
CIRCUIT DESCRIPTION
The airbag system is equipped with a voltage±increase circuit (DC±DC\
converter) in the center airbag
sensor assembly in case the source voltage drops.
When the battery voltage drops, the voltage±increase circuit (DC±DC c\
onverter) functions to increase
the voltage of the airbag system to normal voltage.
The diagnosis system malfunction display for this circuit is different to other circuits±when the airbag
warning light remains lit up and the diagnostic code is a normal code, source voltage d\
rop is indicated.
Malfunction in this circuit is not recorded in the center airbag sensor assembly, and approx. 10 se-
conds after the source voltage returns to normal, the airbag warning lig\
ht automatically goes off.
Code No.
Diagnosis
(Normal)Source voltage drop.
DIAGNOSTIC CHART
Preparation.
Does airbag warning light turn on after
approx. 10 seconds?
Check battery and charging system
(See page CH±1). 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.
WIRING DIAGRAM
AB±40SRS 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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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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*1: ªOº mark means ªO/D OFFº light blinks once every 2 seconds.\
ªXº mark means ªO/D OFFº light never
blinks.
*2: ªOº mark means the ECM memorizes the malfunction code if the ECM detects the diag. trouble \
code
detection condition.
*3: This indicates items for which ª2 trip detection logicº is use\
d. With this logic, when a logic malfunction
is first detected, the malfunction is temporarily stored in the ECM memory. If the same case is detected
again during the second drive test, this second detection causes the O/F\
OFF Light to blink.
The 2 trip repeats the same mode twice. (However, the IG switch must be turned OFF between the 1st trip
and 2nd trip.)
HINT:

If the malfunction returns to normal while a malfunction warning is being \
output, the O/D OFF indicator
light stops blinking and goes off.
However, the malfunction code is retained in memory until it is cleared from me\
mory.

If the diagnosis system outputs a malfunction code even though the O/D OFF indicator was not
blinking, there is intermittent trouble. Check all the connections in the circuit\
s corresponding to that
code.

If the vehicle speed sensors No.1 and No.2 happen to fail simultaneously\
, the ECM will neither alert
the driver by blinking the O/D OFF indicator nor record any diagnostic t\
rouble code. It will, however,
decide that the vehicle can be driven only in 1st and none of the other gears, shifting \
upwards will then
be prohibited.

Codes 46, 62, 63 and 64 are limited to short or open circuits in the electric\
al system comprised of the
solenoids, wire harnesses and connectors. The ECM is unable to detect mechanical t\
rouble (sticking,
for example) in the solenoid valves.
AT±62
±
A304E (1UZ±FE) AUTOMATIC TRANSMISSION TROUBLESHOOTING
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SRS AIRBAG
(See page AB±2)
The LEXUS SC300 is equipped with an SRS (Supplemental Restraint System)\
airbag.
Failure to carry out service operations in the correct sequence could cause the airbag system to deploy,
possibly leading to a serious accident.
When removal or installation of airbag parts and the yellow wire harness\
and connector for the airbag is
necessary, refer to the precautionary notices in the AB section before performing\
the operation.

Work must be started after 20 seconds or longer from the time the ignition switch is set to the LOCK
position and the negative (±) terminal cable is disconnected from the batte\
ry.
(The airbag system is equipped with a back±up power source so that if wor\
k is started within 20 se-
conds of disconnecting the negative (±) terminal cable of the batte\
ry, the airbag may be deployed.

To avoid erasing the memory of each memory system, never use a back±up power supply from
outside the vehicle.

Before repairs, remove the airbag sensors if shocks are likely to be applied t\
o the sensors during
repaires.

The front airbag sensor set bolt has been anti±rust treated. When the\
sensor is removed, always
replace the set bolt with a new one.

If the front airbag sensors, center airbag sensor or steering wheel pad ha\
ve been dropped, or if there
are cracks, dents or other defects in the case, bracket or connector, replace them with new ones.

Never use airbag parts from another vehicle. When replacing parts, repla\
ce them with new parts.

Do not expose the front airbag sensors, center airbag sensor or steering w\
heel pad directly to hot air
or flames.

The airbag system's wire harness is integrated with the cowl wire harness assembly. The wires for the
airbag wire harness are encased in a yellow corrugated tube. All the connector\
s for the system are
also a standard yellow color. If the airbag system wire harness becomes disconnected or the
connector becomes broken due to an accident, etc., repair or replace it as shown \
on page AB±20.

The steering wheel must be fitted correctly to the steering column with the\
spiral cable at the neutral
position; otherwise, cable disconnection and other troubles may result. \
Refer to page AB±14 of this
manual concerning correct steering wheel installation.

When removing the steering wheel pad or handling a new steering wheel pad, i\
t should be placed with
the pad top surface facing up. In this case, the twin±lock type connector lock lever should be in the
locked state and care should be taken to place it so the connector will not be damaged. (\
Storing the
pad with its metallic surface up may lead to a serious accident if the a\
irbag inflates for some reason.)

Grease should not be applied to the steering wheel pad and the pad should not \
be cleaned with
detergents of any kind.

Store the steering wheel pad where the ambient temperature remains below 93 C (200 F), without
high humidity and away from electrical noise.

Information labels are attached to the periphery of the airbag component\
s. Follow the notices.

When the ignition switch is at ACC or ON and the airbag warning light remains on, the cent\
er airbag
sensor assembly has detected a malfunction code. (See page AB±30).
BO±8
±
BODY General Information
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2. INSPECT BRAKE WARNING LIGHT(a) Disconnect the connector from the brake fluid warningswitch.
(b) Release the parking brake pedal.
(c) Connect terminals on the wire harness side of the level warning switch connector.
(d) Start the engine, check that the warning light lights up.
If the warning light does not light up, test the bulb or wire har-
ness.
(Parking Brake Switch)
REMOVAL AND INSTALLATION OF PARKING
BRAKE SWITCH
1. REMOVE PARKING BRAKE SWITCH
(a) Remove the driver's seat.
(See page BO±58)
(b) Disconnect the connector and remove switch.
2. INSTALL PARKING BRAKE SWITCH For installation follow the removal procedure in reverse.
INSPECTION OF PARKING BRAKE SWITCH
1. INSPECT PARKING BRAKE SWITCH
(a) Check that there is continuity between terminal andswitch body with the switch ON (switch pin released).
(b) Check that there is no continuity between terminal and switch body with the switch OFF (switch pin pushed in.)
If continuity is not as specified, replace the switch or inspect
ground point.
2. INSPECT BRAKE WARNING LIGHT (a) Disconnect the connector from the parking brake switchand brake fluid warning switch.
(b) Ground terminal on the wire harness side connector.
(c) Start the engine, check that the warning light lights up.
If the warning light does not light up, test the bulb or inspect
wire harness.
BE±116
±
BODY ELECTRICAL SYSTEM Combination Meter
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