1991 LEXUS SC400 airbag

567 8
21 LEXUS SC300(
Cont ' d )
AIR BAG
CHA RGE
OIL
OIL LEVEL COOLANT
LEVEL REAR
LI GHT
PWR
ABS TRAC
TRAC OFF
CRUISE WASHER
O/ D OFF
FUEL
SEAT BELTP
R N D 2 L
A
C
C A
A
B
B
B
C
C
C
C
C
C
C
B C
C
B
B
BA
B
A
A
C
CA A A A A A A A
C
C
C
C C C A C C B B B B
B A A C C
10 : 00
BK 1E
18 3D
10
3A
1
1J
1 1K
12
IH IF ED
IK1
8
IK2 IK1
9
1
E
3
E
2
E
1
D
BU110
BU1
3
BU1
4 11
11
1
14
19
8
18
11
13 6
18
17
16
20
19
15
13
3
15 5
1
20 9
18 8
11
87 1 2 3 4 5 16 17
2
3
4
5 10 9
12 23 12 4 17 16 7
6
15
10 22 21
W± R
RY
B±O
Y±B
V± R
V±Y
R±W
L±R
W
R± Y B
V±W V
R
L±R
P±L
Y±B
B±Y
B± W
W±B BR
B
W± B W± B BR±B
Y± G
B
Y±G
BR±B
W± B
W±B
W±B
BR±B W± B BR
Y±G
WATER
TEMP.HI GH BEAM TURN
LH
RH
BRAKE DOOR
TACHO
TRI P
SPEED
ILLUMINATIONCHECK±
ENGINE
FUEL
See Taillight and
St op Light Sy stem
<4±6><5±6>
SeeEngineControlSystem
<2±3>
Se e ABS Sy st e m< 8± 7> < 9± 3>
See Cruise Control System
< 16±3>Se e ABS an d Tr act io n
Control System< 8±7>
SeeECTandA/TIndicator
System< 3±5>
D
F1 7 , F18 E
FUEL SENDER Y±B
B±Y
B±W 24
See SRS Airbag System< 15±4>
See Charging Sy stem< 1±2>
See Headlight Sys tem< 4±1> < 5±1>
See Turn Signal and
Hazard Warning
Light Sy stem< 7±3>
See ECT System< 3±5>
From Neutr al St art SW< 1±3>
See Interier Light System< 6±3> From Igniter º TACº < 1±5>
To Engine and ECT ECU< 2±7>
To Cruise Control ECU< 16±3>
To PPS ECU< 15±2> See Illumination System
<4±7><5±7>
See ECT and A/T Indic ator
Syst em< 3±6>
See Unlock and Seat Belt
Warning Syst em< 4±4> < 5±4>
W3
WATER TEMP.
SENDER
Combination Meter
1
COMBINATION METER C12 , C13 , C14
A
AB IG1
8
Under the
c ent er
pillar LH Under the
as htr ay LH
Lef t
kick panelRear side of
c ylinder head RH
C
2
G 2
F
1
F 14
L±R
P
P
SH OR T C ON NE CT OR
S2 2 G , S23 F L±R
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244
Rear Window Defogger
and Mirror Heater
Remote Control Mirror
Seat Heater
Shift Lock
SRS AIRBAG
Starting
Taillight and
Stop Light
Theft Deterrent and
Door Lock Control
Turn Signal and Hazard
Warning Light
Wiper and Washer
Wireless Door Lock
Remote Control
Horn
Ignition
Illumination
Interior Light
Liquid Crystal Inner
Rear View Mirror
Moon Roof
Power Seat
(Driver's)
Power Source
Power Window
PPS (Progressive
Power Steering
Radio and Player
ABS and
Traction Control
Automatic
Air Conditioner
Auto Antenna
Back±Up Light
Cellular Mobile
Telephone
Charging
Cigarette Lighter
Combination Meter
Cruise Control
Headlight and Light Auto
Turn Off (for USA)
Headlight
(for Canada) ECT and
A/T Indicator
4±2 16±2 7±2
3±2 21±2 3±8
14±4
18±2 19±4 (w/o CD Player)
20±8 (w/ CD Player)9±2 8±2
4±7 (for USA)
5±7 (for Canada)11±2
12±311±5 (w/ Driving
Position Memory)11±7 12±1 1±5 13±2
6±2 15±2 14±2
13±2
17±7 7±3 17±2 15±3
1±315±2
Power Tilt and
Power Telescopic12±2
Power Seat (Passengerºs
and Electric Tension Header
5±2 2±2
Cornering Light ABS (Anti±Lock
Brake System)
22±2
Engine Control Unlock and Seat
Belt Warning
1±2
23±2 (w/o Driving
Position Memory)
1 23±119±2 (w/o CD Player
20±2 (w/ CD Player
14±310±2 (w/ Memory)
5±7 (w/o Memory)
4±3 (for USA)
5±3 (for Canada) 4±5 (for USA)
5±5 (for Canada)
OVERALL ELECTRICAL WIRING DIAGRAM
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46
POWER SOURCE (Current Flow Chart)*1: USA
*2: CANADA
60
216
226
192178
226 90 144 134 216 102 202
208
212 90
167
A2 A15 C6 B2
B1
A10 A14 A12 A17A13 A23 A24 A25 A32 C11 B3 B4 B6 C3 C10C7
A21
Blower Resistor Auto Antenna Motor
And Relay A/C Magnetic Clutch
Alternator
A/C Control Assembly
A/C Power Transistor
A/T Indicator Light
(for Shift Lever) A/C Control SW and
Radio SWABS ECU
ABS and Traction ECUBrake Fluid Level SW
Blower Motor
Center Airbag Assembly Check Connector
Cornering Light LH
Cigarette Lighter Back±Up Light SW Buckle SW LHABS and Traction ECUCornering Light RH
190
226 22690
126
226 10168
134
144
178


* These are the page numbers of the first page on which the related system\
is shown.
The part indicated is located somewhere in the system, not necessarily o\
n the page indicated here. *Page Nos. of
Related Systems
Parts
Code or
Location
CB or Fuse
50A DEFOG
30A DOOR
30A POWER
15A STOP
15A ECU±B
10A MIR±HTR
10A HEATER
20A TURN
20A WIPER
10A GAUGE
15A ECU±IG
7.5A ENGINE
7.5A IGN
15A CIG
7.5A RADIO No.2
15A TAIL
7.5A PANEL
7.5A ST
15A TEL
10A DOME
20A RADIO No.1
25A HAZ±HORN
30A EFI
7.5 ALT SENCING
15A HEAD LH*1
15A HEAD RH*1
15A HEAD LH±LWR*2
15A HEAD RH±LWR*2
15A HEAD LH±UPR
15A HEAD RH±UPR
60A HEATER
7.5A TRAC
15A SEAT±HTR
Location
[LOCATION](1): J/B No. 1 (See page 20)(2): R/B No. 2 (See page 19)(3): R/B No. 4 (See page 23)
20
19 22
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47
216182
216
178
216
129 104 144 10260
90
216 62
68
11 2
148
104
111 200 148 148 190
D1
C16 C24
C15 C19 C23 C22
C12
C13
C14C14
C13
C12
Airbag W arning Light
Charge Warning Light
Dimmer SW [Comb. SW]Cruise Control Indicator Light
[Comb. Meter]A/T Indicator Light
[Comb. Meter]
Combination Meter
Rear Lights Warning Light Turn Signal Indicator Light
[Comb. Meter] High Beam Indicator Light
[Comb. Meter]
Check Engine Warning Light
Open Door Warning Light
Traction Indicator Light
ABS Warning Light
[Comb. Meter] Seat Belt Warning LightABS Warning Light and T raction
Off Indicator Light [Comb. Meter]
Coolant Level Warning LightCruise Control ECU Turn Signal SW
[Comb. SW]
Wiper and Washer SW
[Comb. SW]
Choke Coil
Crutch Start SW
Cruise Control Clutch SW
Diode (for Brake Fluid Level)Light Control SW
[Comb. SW] Horn SW [Comb. SW]Combination MeterCornering Light SW
[Comb. SW]
C12 80
82
216
216 216 98
86
216134
216
216 216 184
216
80
90
102 80
90
102
68
94
134
148
216
(4)
: R/B No. 5 (See page ) 22
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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.
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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 is disconnected, the short spring plate
automatically connects the power source and grounding
terminals of the squib to preclude a potential difference
between the terminals.
2. ELECTRICAL CONNECTION CHECK MECHANISMThis mechanism is designed to electrically check if
connectors are connected correctly and completely.
The electrical connection check mechanism is designed so
that the connection detection pin connects with the
diagnosis terminals when the connector housing lock is in
the locked condition.
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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 ENGINE AND
ECT ECU(
E1 )
CHECK
CONNECTOR
TDCL
FRONT AIRBAG
SENSOR LH FRONT A I RBA G
SENSOR RH
AIRBAG SQUIBSPIRAL
CA BLE
CENTER AIRBAG SENSOR ASSEMBLY
BR
W±B W±BL
Y B
GR
WR
L
Y
B
GR
WR
BR W±B
BR BR BR B±Y P±BP±B
B±Y
P±B
B±Y B±Y W±RW±R
L±R
B±O
FROM POWER SOURCE SYSTEM
(
SEE PAGE 56 )
AIRBA G WA RNING
LIGHT
[COMB. METER]
C10
F1 F2 A2 9 C3
T6 C12
E2 0
1G
9 912
IF ED 1G
7
EC
LA TC
1E
41E 3
3B
2
3H
12
3E
3
3E
10
1J
1 3A
3
1G
4
1G
3 3A
73D 11
B±Y
P±B
B±Y
P±B
B±Y
W±B
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181
THE SRS (SUPPLEMENTAL RESTRAINT SYSTEM) AIRBAG IS A DRIVER PROTECTION DEVICE WHICH HAS A SUPPLEMENTAL ROLE
TO THE SEAT BELTS.
CURRENT FLOWS CONSTANTLY TO TERMINAL 6 OF THE CENTER AIRBAG SENSOR ASSEMBLY. WHEN THE IGNITION SW IS
TURNED TO ACC OR ON, CURRENT FROM THE CIG FUSE FLOWS TO TERMINAL 14 OF THE CENTER AIRBAG SENSOR ASSEMBLY.
ONLY WHEN THE IGNITION SW IS ON DOES THE CURRENT FROM THE IGN FUSE TO TERMINAL 7 .
IF AN ACCIDENT OCCURS WHILE DRIVING, DECELERATION CAUSED BY A FRONTAL IMPACT IS DETECTED BY EACH SENSOR AND
SWITCH, AND WHEN THE FRONTAL IMPACT EXCEEDS A SET LEVEL (WHEN THE SAFING SENSOR BUILT INTO THE CENTER AIRBAG
SENSOR ASSEMBLY IS ON AND THE CENTER AIRBAG SENSOR IS ON, FRONT AIRBAG SENSORS ARE OFF), CURRENT \
FROM THE
CIG OR IGN FUSE FLOWS TO TERMINAL 11 OF THE CENTER AIRBAG SENSOR ASSEMBLY " TERMINAL 1 OF THE AIRBAG SQUIB "
SQUIB " TERMINAL 2 " TERMINAL 10 OF CENTER AIRBAG SENSOR ASSEMBLY " TERMINAL 8, TERMINAL 13 OR BODY GROUND
" GROUND.
WHEN THE SAFING SENSOR BUILT INTO THE CENTER AIRBAG SENSOR ASSEMBLY IS ON AND THE FRONT AIRBAG SENSOR LH OR
RH IS ON, CENTER AIRBAG SENSOR IS OFF AND CURRENT FROM THE CIG OR IGN FUSE FLOWS TO TERMINAL 11 OF THE CENTER
AIRBAG SENSOR ASSEMBLY " TERMINAL 1 OF THE AIRBAG SQUIB " SQUIB " TERMINAL 2 " TERMINAL 10 OF CENTER AIRBAG
SENSOR ASSEMBLY " TERMINAL 3 OR 4 " TERMINAL 1 OF FRONT AIRBAG SENSOR " TERMINAL 2 " TERMINAL 2 OR 5 OF
CENTER AIRBAG SENSOR ASSEMBLY " TERMINAL 8, TERMINAL 13 OR BODY GROUND " GROUND , WHEN THE SAFING SENSOR
BUILT INTO THE CENTER AIRBAG SENSOR ASSEMBLY IS ON, AND THE FRONT AIRBAG SENSOR LH OR RH IS ON AND CENTER
AIRBAG SENSOR IS ON ONE OF THE ABOVE±MENTIONED CIRCUITS IS ACTIVATED SO THAT CURRENT FLOWS TO THE AIRBAG
SQUIB AND CAUSES IT TO OPERATE. THE BAG STORED INSIDE THE STEERING WHEEL PAD IS INSTANTANEOUSLY EXPANDED TO
SOFTEN THE SHOCK TO THE DRIVER.
: PARTS LOCATION
CODESEE PAGECODESEE PAGECODESEE PAGE
A2928C1228T 629
C 326F 126
C1028F 226
: JUNCTION BLOCK AND WIRE HARNESS CONNECTOR
CODESEE PAGEJUNCTION BLOCK AND WIRE HARNESS (CONNECTOR LOCATION)
1E20INSTRUMENT PANEL WIRE
1G20COWL NO. 2 WIRE
1J20COWL WIRE
3A
3B
3D22INSTRUMENT PANEL WIRE
3E
3H
: CONNECTOR JOINING WIRE HARNESS AND WIRE HARNESS
CODESEE PAGEJOINING WIRE HARNESS AND WIRE HARNESS (CONNECTOR LOCATION)
IK136ENGINE WIRE AND INSTRUMENT PANEL WIRE (RIGHT KICK PANEL)
: GROUND POINTS
CODESEE PAGEGROUND POINTS LOCATION
EC34FRONT SIDE OF INTAKE MANIFOLD
ED34REAR SIDE OF CYLINDER HEAD RH
IF36LEFT KICK PANEL
: SPLICE POINTS
CODESEE PAGEWIRE HARNESS WITH SPLICE POINTSCODESEE PAGEWIRE HARNESS WITH SPLICE POINTS
E2034ENGINE WIRE
SYSTEM OUTLINE
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