light LEXUS SC400 1991 Service User Guide

STANDARD VALUE OF ECU TERMINAL
TerminalsSymbolsWiringColorConditionStandardValue
A14±1A14±7B ER W±BIG OFF10 ~ 14 V
A14±2 A14±3MH MCV R±YIG OFF13 ~ 19

A14±4A14±5MFRSMRECG G±RIG OFF13 ~ 19

A14±6A14±7IG+ ER±L W±BIG ON10 ~ 14 V
Body
A14±7 
Ground Body
E 
Ground Body
W±B 
GroundAlwaysBelow 1

A14±8A14±9FACE DEFW Y±LIG OFF13 ~ 19

A14±15A14±7ACC EL±R W±BTurn ignition switch ACC10 ~ 14 V
A12±2 A14±7REOST EW±G W±B
IG ON and turn headlight control SW
to TAIL position.
Turn Rheostat volume from most
right to left position.
Most
: 0 ~ 14 V
Right

Most
: 10 ~ 14 V
Left
A12 3 A14 7WV EBY WB
Start
the
MAX
Temp. Control Switch:
COLDBelow 1 V
A12±3 A14±7WV EB±Y W±Btheen-
gine MAX
Temp. Control Switch:
HOT10 ~ 14 V
A12 4 A14 7MGC ELR WB
Start the
engine andA/C switch ONBelow 1 V
A12±4 A14±7MGCEL±R W±Bengine andpush AUTO
SWA/C switch OFF10 ~ 14 V
A12 5 A14 7TC EL WBIG ONHLC SW
Rheostat Most
:
Volume RightBelow 1 V
A12±5 A14±7TCEL W±BH.L.C. SW
: TAIL positionRheostat Turn
:
Volume Left10 ~ 14 V
A12±6 A14±7TAIL EG W±BTurn the light control switch to TAILposition10 ~ 14 V
A12±7A14±7LV EYW±BIG ONPush blower SW to change
the blower speed from 1 to
10.Speed 1: 10 ~ 14 V

Speed 10: Below 2 V
A12±8 A14±7BLR EB±R W±BIG ONTurn the blower motorBelow 1.5 V
A12±9 A14±7HR EL±W W±B
IG ON
Turn the blower motorBelow 1 V
IG ONDon't turn the blower motor10 ~ 14 V
A12 10 A14 7RDFGR ERY WBIG ON
Rear defogger switch ONBelow 1 V
A12±10 A14±7RDFGR ER±Y W±BIG ONRear defogger switch OFF10 ~ 14 V
A13±1 A14±7IGN EBW±BStart the engine10 ~ 14 V
AC±32±
AIR CONDITIONING SYSTEM Troubleshooting
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99
Check voltage between terminals S5 and TS of air conditioner
control assembly connector.
(1) Remove console upper panel. (See page
BO-111 ).
(2) Remove A/C control assembly with connec-
tors still connected.
(3) Turn ignition switch ON.Measure voltage between terminals S5 and TS
of air conditioner control assembly connector
when the solar sensor is subjected to an electric
light, the sensor is covered by a cloth.
ConditionVoltage
Sensor subjected to electric light
Sensor covered by a cloth
Below 4 V
4 ±4.5 V
In addition, when the inspection light is gradu-
ally moved away from the sensor, the voltage
increases.
Proceed to next circuit inspection shown on
matrix chart (See page AC-36).However,
when Diag. code 21 is displayed, check and
replace air conditioner control assembly.
Check solar sensor.
(1) Remove solar sensor from dashboard.
(2) disconnect solar sensor connector.
Connect positive (+) lead of ohmmeter to terminal 2
and negative (±) lead to terminal 1 of the solar sensor.
(1) Cover the sensor by a cloth.
(2) Measure resistance between terminals 1 and 2 of solar sensor connector.
(1) Remove the cloth from the solar sensor andsubject the sensor to electric light.
(2) Measure resistance.
Resistance: Approx, 4 k
(continuity)
In addition, as the electric light is moved gradu-
ally away from the sensor the resistance in-
creases.
Replace solar sensor.
Check for open and short in harness and connector between air conditioner
control assembly and solar sensor (See page IN-27).
Repair or replace harness or connector.
Check and replace air conditioner control
assembly.
INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±53
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Check power transistor.
(1) Remove cooling unit (See page BO-107).
(2) Disconnect power transistor connector.
(1) Check test bulb lights up when battery and
resistor are connected to power transistor
connector as left illustration shows.
(2) Measure resistance between terminal 2 and 3
(1) The bulb lights up.
(2)Resistance: 2.0± 2.4 k 
Replace power transistor.
Check for open and short in harness and connector between air
conditioner control assembly and power transistor (See page IN-27).
Repair or replace harness or connector.
Proceed to next circuit inspection shown on matrix
chart (See page AC-36).
INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±79
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No.Gauge reading kPa (kgf/cm2, psi)ConditionProbable cause Remedy
LO: 1.5 ± 2.0(21 ±28, 147 ±196)
HI: 14.5 ± 15.0(206 ±213, 1422 ±1471)
Normal coolingNormally functioning
system
During operation, pressure at low
pressure side sometimes becomes a
vacuum and sometimes normal.Periodically cools
and then fails to
cool.Moisture present in
refrigeration system.(1). Replace receiver
(2). Remove moisturein system through
repeatedly
evacuating air
Inspection of Refrigeration System with Manifold Gauge Set
This is a method in which the trouble is located by using a manifold gauge s\
et. (See ºInstallation of Manifold
Gauge Setº on page AC±15) Read the manifold gauge pressure when the following conditions are es\
tablished:
(a) Temperature at the air inlet with the switch set at RECIRC is 30±35 °C (86±95 °F).
(b) Engine running at 2,000 rpm.
(c) Blower fan speed control switch set at high speed.
(d) Temperature control switch set at max. cool side.
HINT: It should be noted that the gauge indications may vary slightly due to\
ambient temperature conditions.
NOTICE:
w Always recover refrigerant before removing the parts in the refrigerant \
line and evacuating air.
w Evacuate air and charge proper amount of purified refrigerant after installing th\
e parts in the
refrigerant line.
AC±100
±
AIR CONDITIONING SYSTEM Troubleshooting
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RECEIVER
ON±VEHICLE INSPECTION
1. REMOVE THE HEADLIGHT ON THE VEHICLE'S LEFTSIDE
See page BE±37
2. INSPECT FITTINGS FOR LEAKAGE Using a gas leak tester, check for leakage.
If there is leakage, check the tightening torque at the joints.
3. INSTALL HEADLIGHT See page BE±37
REMOVAL OF RECEIVER
1. REMOVE THE HEADLIGHT ON THE VEHICLE'S LEFT
SIDE
See page BE±37
2. RECOVER REFRIGERANT IN REFRIGERATION SYSTEM See page AC±16
3. REMOVE TWO LIQUID TUBES FROM RECEIVER Remove the two bolts and both the tubes from the receiver.
4. REMOVE RECEIVER FROM RECEIVER HOLDER Remove the bolt, then remove the receiver from the receiver
holder.
NOTICE: Cap the open fittings immediately to keep mois-
ture out of the system.
AC±118
±
AIR CONDITIONING SYSTEM Receiver
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INSTALLATION OF RECEIVER
1. INSTALL RECEIVER IN RECEIVER HOLDERInstall the receiver in the receiver holder with the one bolt.
2. INSTALL TWO LIQUID TUBES ON RECEIVER Install the two liquid tubes on the receiver with the two bolts.
Specified torque: 5.4 N Vm (55 kgf Vcm, 4 ft Vlbf)
NOTICE: Do not remove the caps until the tubes are con-
nected.
3. REPLENISH COMPRESSOR OIL IF RECEIVER HAS BEEN REPLACED
Add 20 cc (0.7 fl.oz.)
Compressor oil: ND OIL 6,
SUNISO NO. 5 GS or equivalent
4. EVACUATE AIR IN REFRIGERATION SYSTEM ANDCHARGE WITH REFRIGERANT
See page AC±17
Specified amount: 950 + 50 g (33.44 + 1.76 oz)
5. INSPECT FOR LEAKAGE OF REFRIGERANT
Using a gas leak tester, check for leakage of refrigerant.
If there is leakage, check the tightening torque at the joints.
6. INSPECT A/C OPERATION
7. INSTALL HEADLIGHT See page BE±37
±
AIR CONDITIONING SYSTEM ReceiverAC±119
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5Check harness between center airbag sensor assembly and front airbag
sensor.
(1) Disconnect center airbag sensor assembly
connector.
(2) Using service wires, connect +SR and ±SR, +SL and ±SL on the wire harness side of the
center airbag sensor assembly connector.
Measure resistance between terminals +SR and
±SL, +SL and ±SL of harness side connector of
front airbag sensor.

Lightly touch ohmmeter probes at
position shown in illustration.

Make sure the front airbag sensor con-
nector is properly connected.
Repair or replace harness or connector between
center airbag sensor assembly and front airbag
sensor (See page AB±20).
Replace front airbag sensor connector (See page AB±20)
NG
OK
Resistance: Below 1

AB±72±
SRS AIRBAG Troubleshooting
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Diag. Code 22Airbag Warning Light System Malfunction
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.
The airbag warning light circuit is equipped with an electrical connecti\
on check mechanism which
detects when the connector to the center airbag sensor assembly is not p\
roperly connected.
If the connector to the center airbag sensor assembly is not properly co\
nnected, the airbag warning
light will not light up.
Diagnostic code 22 is recorded when a malfunction occurs in the airbag w\
arning light system.
If an OPEN malfunction occurs in the airbag warning light system, the ai\
rbag warning light does not
light up, so that until the malfunction is repaired, the diagnostic code\
s (including code 22) cannot be
confirmed.
Code No.Diagnosis
22
Open circuit in airbag warning light system.22
Center airbag sensor assembly malfunction.
AB±74±
SRS AIRBAG Troubleshooting
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OKNG
1
2
3
4
5
6
6
OK
OK
YES
YES NG
NG NO
NO
Check connection of center airbag sensor
assembly connector.
Preparation.
Check airbag warning light circuit.
Does airbag warning light come on?
Is new ECU ±B fuse burnt out again? GO to step
Repair.
Repair airbag warning light circuit
(See page BE±150).
Check terminal LA of center
airbag sensor assembly and
electrical connection check
mechanism. If normal, replace
center airbag sensor assembly.
Using simulation method,
reproduce malfunction symptoms
(See page IN±20).
Check harness between ECU ±B fuse and
airbag warning light, and ECU±B fuse and
center airbag sensor assembly. 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.
Check ECU ±B fuse.
DIAGNOSTIC CHART
Troubleshooting for this system is different for when the airbag warning light does not light up and for
when diagnostic code 22 is output. Confirm the problem symptoms first before\
selecting the appropriate
troubleshooting procedure.
HINT: If airbag warning light does not light up, perform the following troub\
leshooting:
±
SRS AIRBAG TroubleshootingAB±75
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Check ECU±B fuse.
NG
OK
1
6Go to step
(1) Disconnect battery negative (±) terminal cable, and wait at least 20 seconds.
(2) Remove steering wheel pad (See page AB±14).
When storing steering wheel pad, keep upper
surface of pad facing upward.
NG
OKRepair.
Check connection of center airbag sensor assembly connector.2
3Preparation.
INSPECTION PROCEDURE
HINT: If airbag warning light does not light up, perform the following troubl\
eshooting:
±
SRS AIRBAG TroubleshootingAB±77
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