reset LEXUS SC300 1991 Service User Guide

METER, ANALOGCurrent flow activates a magnetic
coil which causes a needle to
move, thereby providing a relative
display against a background
calibration.
LED (LIGHT EMITTING DIODE)
Upon current flow, these diodes
emit light without producing the
heat of a comparable light.
IGNITION COIL
Converts low±voltage DC current
into high±voltage ignition current
for firing the spark plugs.
1. SINGLE
FILAMENT
GROUND
The point at which wiring attaches
to the Body, thereby providing a
return path for an electrical circuit;
without a ground, current cannot
flow. Current flow causes a headlight
filament to heat up and emit light.
A headlight may have either a
single (1) filament or a double (2)
filament.
BATTERY
Stores chemical energy and
converts it into electrical energy.
Provides DC current for the auto's
various electrical circuits.
CAPACITOR (Condenser) A small holding unit for temporary
storage of electrical voltage.
CIRCUIT BREAKER Basically a reusable fuse, a circuit
breaker will heat and open if too
much current flows through it. Some
units automatically reset when cool,
others must be manually reset.
DIODE A semiconductor which allows
current flow in only one direction.
DIODE, ZENER A diode which allows current flow
in one direction but blocks reverse
flow only up to a specific voltage.
Above that potential, it passes the
excess voltage. This acts as a
simple voltage regulator.
FUSE A thin metal strip which burns
through when too much current
flows through it, thereby stopping
current flow and protecting a
circuit from damage.
FUSIBLE LINK A heavy±gauge wire placed in
high amperage circuits which
burns through on overloads,
thereby protecting the circuit.
The numbers indicate the cross±
section surface area of the wires. HORN
An electric device which sounds a
loud audible signal.
LIGHT Current flow through a filament
causes the filament to heat up
and emit light.
METER, DIGITAL Current flow activates one or
many LED's, LCD's, or fluorescent
displays, which provide a relative
or digital display.
MOTOR A power unit which converts
electrical energy into mechanical
energy, especially rotary motion.
CIGARETTE LIGHTER
An electric resistance heating
element.
DISTRIBUTOR, IIA Channels high±voltage current
from the ignition coil to the
individual spark plugs. 2. DOUBLE
FILAMENT
HEADLIGHTS
FUEL
(for High Current Fuse or
Fusible Link)
(for Medium Current Fuse)
M
16
GLOSSARY OF TERMS AND SYMBOLS
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OVERALL ELECTRICAL WIRING DIAGRAM
1234
21 LEXUS SC300 (
Cont . ne xt pa ge )
4 ACC
IG1
ST 1
IG2
AM1
3
2
6
11 AM2
1J
7
1B
4 16 IE1
20 IK110 IK2
1IE1
1J
31J 51J821B 2
1E
1E
18
1E 1H1E 2 1E
131B
IG1 20 3D
3A 4
3D
2
3C
6
3A
2
3F
1 2 1 6
3F 5
3C
5
3A
IK16
IK1 7
10 IJ1
IE110
IG118
EB
19 IG1
ED EA 13 IE2 14 IG3 W± R
R
Y
B± O Y± B
V±R V± Y
R± W
L±R
W
R±Y B
V±W V
R
L±R
P± L
R
L±R L±R
P± L
P± L
Y
B±O B±YP±L
W± L
R± W
B
W± B R±W
B
W
W
W±L
W± L W±L
W
W±R
Y±B
V±R
V± Y
R±WV±Y V± R Y±B
W± R
W
W± R
B± O
R±W R± W
B
B
R±W R±W
R±W V±Y
BR
W± B
R±W Y
W±B Y
R4713
21 11
4
12
8
7
9
2
1
2
340A IGSW
100A AM1
120A ALT
60A MAIN
30A INJ
30A AM2
14
9 I15
IGNITION SW
7. 5A I GN
10A GAUGE
15A CIG
10A DOME
15A ECU±B
From ABS ECU
<9±2>
From ABS ECU
< 8±5>
(
* 1 )
(
* 2)
6
BATTERY
F9
FUSE BLOCK
12
O2
OI L P RE SS URE SW
C5
COOLANT LEUEL
WARNING SW E6
ENGI NE OI L L EVEL
WARNING SW
P3
PARKI NG
BRAKE SWD2
DIODE
(f or Par king
Brake )
B1
BRAKE FLUID
LEVEL SW
B
B
R±W R±WR±W
R±W
B
B B
( Canada )
(
Canada )
( US A )
(USA )
(
US A )
(
US A )
(
Canada )
(
Canada )(
Canada )
(
* 2
) (
* 1)
(
US A )(
US A)
(
USA )
R±W
R± W
Fro m Dayt i me
Running Light
Relay< 4±4>
Fr om Cr uise Control
ECU< 16±2> T1 5
TRIP SW AND THEFT DETERRENT
I NDI CA TOR L I GHT
S3
SPEED SENSOR No. 1
From Tr act ion ECU
<8±7>
2
W
12 12 2 54 11 13 *
1: (
w/ Tr action Contr ol )
* 2: (
w/oTractionControl )
Power
Source Combination Meter
R±WL±R
R
4 3
SECURITY
M
H
SET
RESET A/ B
W1
WASHER
LEVEL SW
P± L
L±R
R W± R
From ABS ECU
<8±5>
( * 1)
R
R
10 11 12 13 17 18 19 20 21 12345 6789
14 15 16 12 34 56 78
9 10 1112 13 14 1516 1718
17 18
1 2345 6789 10
23
22
21
20
19
15
14
13
12
11 16
AB C
C12 C13 C14 COMBINATION METER
1 1
23
DE
FUEL SENDER
F1 7 F1 8
Rear side of
c ylinder head LH Fr ont side of
right fender Fr ont s ide of
left f ender
2
1
2 2
1 1
1
B
S HORT CONNE CTOR
1
2 12F
S23
G
S22
7BU1
From Tilt and
Power Telesc opic
ECU< 11±2>
GR
B
( M/T ) 3
G±B
From Theft Det err ent and
Door Lock ECU< 17±2>
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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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