1991 LEXUS SC400 Service Repair Manual

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Page 4049 of 4087

LEXUS SC400 1991 Service Repair Manual
190
SEAT HEATER
1
32 1
32
1
32 1
32
4
3A
1 3H
14
1E
18
1J
1 IG2
10
BY13
BU1 2 Bb1
14
IF BK BL
Ba1
12
FROM POWER SOURCE SYSTEM
(
SEE PAGE 56 )
15A
SEAT±HTR
1
GLL G
B
B
W±B
G
Y
W Y
W W±B
W±B
W±B
W

Page 4050 of 4087

LEXUS SC400 1991 Service Repair Manual
191
T12 SEAT HEATER SW
7±GROUND : APPROX. 12 VOLTS WITH SW AT ON POSITION
8±GROUND : ALWAYS CONTINUITY
: PARTS LOCATION
CODESEE PAGECODESEE PAGECODESEE PAGE
S1532S1732S24B29
S1632S1832T12A29
: R

Page 4051 of 4087

LEXUS SC400 1991 Service Repair Manual
188
SHIFT LOCK
1E
21E 17 1I 10
7 8 SHIFT LOCK
CONTROL SW
SHIFT LOCK
SOLENOID
TIMER
3
2 4
5
1
P1
±P
P2
SLS±
SLS+
1 2
IF 15A
CIG
15A
ECU±IG 15A
STOP
KEY INTERLOCK
SOLENOID
[IGNITION SW] STOP LIGHT
S

Page 4052 of 4087

LEXUS SC400 1991 Service Repair Manual
189
WHEN THE IGNITION SW IS TURNED TO ACC POSITION THE CURRENT FROM THE CIG FUSE FLOWS TO TERMINAL 1 OF THE SHIFT
LOCK ECU, IN THE ON POSITION, THE CURRENT FROM THE ECU±IG FUSE FLOWS TO TERMINA

189
WHEN THE IGNITION SW IS TURNED TO ACC POSITION THE CURRENT FROM THE CIG FUSE FLOWS TO TERMINAL 1 OF THE SHIFT
LOCK ECU, IN THE ON POSITION, THE CURRENT FROM THE ECU±IG FUSE FLOWS TO TERMINAL 5 OF THE ECU.
1. SHIFT LOCK MECHANISM
WITH THE IGNITION SW ON, WHEN A SIGNAL THAT THE BRAKE PEDAL IS DEPRESSED (STOP LIGHT SW ON) AND A SIGNAL THAT
THE SHIFT LEVER IS PUT IN ªPº RANGE (CONTINUITY BETWEEN P1 AND P OF THE SHIFT LOCK CONTROL SW) IS INPUT TO THE
ECU, THE ECU OPERATES AND CURRENT FLOWS FROM TERMINAL 5 OF THE ECU " TERMINAL SL+ OF THE SHIFT LOCK
SOLENOID " SOLENOID " TERMINAL SL± " TERMINAL 3 OF THE ECU " GROUND. THIS CAUSES THE SHIFT LOCK SOLENOID TO
TURN ON (PLATE STOPPER DISENGAGES) AND THE SHIFT LEVER CAN SHIFT INTO RANGE OTHER THAN THE ªPº RANGE.
2. KEY INTER LOCK MECHANISM
WITH THE IGNITION SW ON OR ACC POSITION, WHEN THE SHIFT LEVER IS PUT IN ªPº RANGE (NO CONTINUIT\
Y BETWEEN P2 AND P
OF SHIFT LOCK CONTROL SW), THE CURRENT FLOWING FROM TERMINAL 2 OF THE ECU " KEY INTER LOCK SOLENOID IS CUT
OFF. THIS CAUSES THE KEY INTER LOCK SOLENOID TO TURN OFF (LOCK LEVER DISENGAGES FROM LOCK POSITION) AND THE
IGNITION KEY CAN BE TURNED FROM ACC TO LOCK POSITION. IF THE IGNITION IS LEFT IN ACC OR ON POSITION WITH THE SHIFT
LEVER IN OTHER THAN ªPº RANGE, THAN AFTER APPROX. ONE HOUR THE ECU\
OPERATES TO RELEASE THE LOCK.
S10 SHIFT LOCK ECU
1±GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ACC OR ON POSITION
5±GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
3±GROUND : ALWAYS CONTINUITY
4±GROUND : APPROX. 12 VOLTS WITH BRAKE PEDAL DEPRESSED
S12 STOP LIGHT SW
2±1 : CLOSED WITH BRAKE PEDAL DEPRESSED
: PARTS LOCATION
CODESEE PAGECODESEE PAGECODESEE PAGE
I1529S1029S1229
: JUNCTION BLOCK AND WIRE HARNESS CONNECTOR
CODESEE PAGEJUNCTION BLOCK AND WIRE HARNESS (CONNECTOR LOCATION)
1E20INSTRUMENT PANEL WIRE
1H
1I20COWL WIRE
1J
20COWL WIRE
3A
3G22INSTRUMENT PANEL WIRE
3H
: CONNECTOR JOINING WIRE HARNESS AND WIRE HARNESS
CODESEE PAGEJOINING WIRE HARNESS AND WIRE HARNESS (CONNECTOR LOCATION)
IG136INSTRUMENT PANEL WIRE AND COWL WIRE (R/B NO. 5)
: GROUND POINTS
CODESEE PAGEGROUND POINTS LOCATION
IF36LEFT KICK PANEL
X 78 12345
12
I15 S 10 S 12
BLACK
SYSTEM OUTLINE
SERVICE HINTS
WhereEverybodyKnowsYourName

Page 4053 of 4087

$LEXUS SC400 1991 Service Repair Manual 177 SRS AIRBAG NOTICE: When inspecting or repairing the SRS AIRBAG, perform the operation in accord\ ance with the following precautionary instructions and the procedure and precautions in the Repair$

177
SRS AIRBAG
NOTICE: When inspecting or repairing the SRS AIRBAG, perform the operation in accord\
ance with the
following precautionary instructions and the procedure and precautions in the Repair Manual for the applicable
model year.
Malfunction symptoms of the airbag system are difficult to confirm, so the diagnostic codes become the most
important source of information when troubleshooting.
When troubleshooting the airbag system, always inspect the diagnostic codes before disconnecting the
battery.
Work must be started after 30 seconds or longer from the time the Ignition SW is set to the ªLOCKº position
and the negative (±) terminal cable is disconnected from the battery.
(The airbag system is equipped with a back±up power source so that if work is started within 30 seconds of
disconnecting the negative (±) terminal cable of the battery, the airbag may be deployed.)
When the negative (±) terminal cable is disconnected from the battery, memory of the clock and audio systems
will be cancelled. So before starting work, make a record of the contents memorized by each me\
mory system.
Then when work is finished, reset the clock and audio system as before.
When the vehicle has tilt and telescopic steering, power seat, outside r\
ear view mirror and power shoulder
belt anchorage, which are all equipped with memory function, it is not possible to make a record of the memory
contents. So when the operation is finished, it will be necessary to explain this\
fact to the customer, and
request the customer to adjust the features and reset the memory.
To avoid erasing the memory of each memory system, never use a back±up \
power supply from outside the
vehicle.
When removing the steering wheel pad or handling a new steering wheel pad, keep the pad upper surfa\
ce
facing upward. Also, lock the lock lever of the twin lock type connector\
at the rear of the pad and take care
not to damage the connector.
(Storing the pad with its metallic surface up may lead to a serious accident if \
the airbag inflates for some
reason).
Store the steering wheel pad where the ambient temperature remains below\
93 °C (200 °F), without high
humidity and away from electrical noise.
Never use airbag parts from another vehicle. When replacing airbag parts\
, replace them with new parts.
Never disassemble or repair the steering wheel pad, center airbag sensor asse\
mbly or front airbag sensors.
Before repairing the body, remove the airbag sensors if during repair shocks are likely to be app\
lied to the
sensors due to vibration of the body or direct tapping with tools or oth\
er parts.
Do not reuse a steering wheel pad or front airbag sensors.
After evaluating whether the center airbag sensor assembly is damaged or not, decide whether or not to reuse
it. (See the Repair Manual for the method for evaluating the center airbag\
sensor assembly.)
When troubleshooting the airbag system, use a high±impedance (Min. 1\
0k W/V) tester.
The vehicle wiring harness exclusively for the airbag system is distinguish\
ed by corrugated yellow tubing, as
are the connectors.
Do not measure the resistance of the airbag squib.
(It is possible this will deploy the airbag and is very dangerous.)
If the wire harness used in the airbag system is damaged, replace the wh\
ole wire harness assembly.
When the connector to the airbag front sensors can be repaired alone (when \
there is no damage to the wire
harness), use the repair wire specially designed for the purpose.
(Refer to the Repair Manual for the applicable Model year for details o\
f the replacement method.)
INFORMATION LABELS (NOTICES) are attached to the periphery of the airbag componen\
ts. Follow the
instructions on the notices.
WhereEverybodyKnowsYourName

Page 4054 of 4087

$LEXUS SC400 1991 Service Repair Manual 178 SRS AIRBAG The airbag system has connectors which possess the functions described belo\ w:1. AIRBAG ACTIVATION PREVENTION MECHANISMEach connector contains a short spring plate. When the connector$

Page 4055 of 4087

LEXUS SC400 1991 Service Repair Manual
179
3. CONNECTOR TWIN±LOCK MECHANISMWith this mechanism connectors (male and female
connectors) are locked by two locking devices to increase
connection reliability. If the primary lock is incompl

Page 4056 of 4087

LEXUS SC400 1991 Service Repair Manual
180
SRS AIRBAG
1G
10 1G 6
1G
11E 13
10 11
IK1
10 IK1 23
IK 1
1
4
+SL
5±SL
3+SR
2±SR
11D+
10D±
13E1
8E2
3E1
3E1
7
IG2 14
ACC 6
+B
12AB 4
TC 11
TC 5
AB
121212 7. 5A
IGN
15A
CIG 15A
ECU±B
FROM ENGIN

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