1991 LEXUS SC400 low beam

Parts Replacement (Turn Signals)
(Cornering Light)
REPLACEMENT OF CORNARING LIGHT
1. REMOVE CORNARING LIGHT(a) Disconnect negative (±) terminal from the battery.
CAUTION: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ºLOCKº position and negative (±) terminal
cable is disconnected from the battery.
(b) Remove front under cover. (See page BO±92 )
(c) Remove a screw and two nuts.
(d) Remove cornaring light from bumper.
(e) Disconnect connector.
2. INSTALL CORNARING LIGHT For installation follow the removal procedure in reverse.
(Front Turn Signal Light)
REPLACEMENT OF FRONT TURN
SIGNAL LIGHT
(See page BE±37 )
HINT: Replacement of Headlight (LO±Beam)
(Rear Combination Light)
(See page BE±56 )
±
BODY ELECTRICAL SYSTEM Lighting SystemBE±67
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8. INSPECT CHARGING CIRCUIT WITH LOAD(a) With the engine running at 2,000 rpm, turn on the highbeam headlights and place the heater blower switch at
ºHIº.
(b) Check the reading on the ammeter.
Standard amperage: 30 A or more
If the ammeter reading is less than standard amperage, re-
pair the alternator. (See page CH±9)
HINT: With the battery fully charged, the indication will some-
times be less than standard amperage.
9. REINSTALL ENGINE UNDER COVER
CH±8
±
CHARGING SYSTEM On±Vehicle Inspection
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8. INSPECT CHARGING CIRCUIT WITH LOAD(a) With the engine running at 2,000 rpm, turn on the highbeam headlights and place the heater blower switch at
ºHIº.
(b) Check the reading on the ammeter.
Standard amperage: 30 A or more
If the ammeter reading is less than standard amperage, re-
pair the alternator. (See page CH±9)
HINT: With the battery fully charged, the indication will some-
times be less than standard amperage.
9. REINSTALL ENGINE UNDER COVER
CH±8
±
CHARGING SYSTEM On±Vehicle Inspection
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80
HEADLIGHT (FOR USA)
18
97 13
OFF
TA I L
HE AD
LOW
HIGH
FL AS H
LIGHT
CONTROL SW
DIMMER SW
COMBINATION
SW C15
1J
1
2
22
4
1K
5
2
1 21
2 1
21
2
IF
I8
I5
E2
E1
IJ
IE1
19 IG1 8
44
4
6 31 19 15
6
2
6 13
7
16
20
42
5
7
IG1
9
IE1
6
IE1
12
W
R±W
W
R±W
R±W R±W R±B
R±B
R±W
R±L
R±G R±Y
W
W±B
W±B
W±B
W±B
W±BR W±B
RR R
W±B
W±B
R±W
R±Y
W±G
60A MAIN
15A
HEAD
(
LH ) 15A
HE AD
(
RH )
FUSE BLOCK
HIGH BEAM
INDICATOR LIGHT
[COMB. METER]
INTEGRATION
RELAY
LO RH HI RH HI LH LO LH
BATTERY
HEADLIGHT
RELAY
FROM CORNERING
LIGHT RELAY I16
C13 H4 H2 H1 H3
F9
HEADLIGHT
DIODE
E3
I15 IE1
5
R±Y
R±Y
W±B
R
R
R
R
R R
R±Y
R±G
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OVERALL ELECTRICAL WIRING DIAGRAM
1234
4 LEXUS SC300
1J
7 221J
81B2
4
1B
5
1B
4 1K
11
22
22
44
1I 1E
3
4
1 2 23
1
5
4
ACC
IG1
ST1
AM1 3
2
1 21
2 1
21
2
19 IE1 12 IE1 5IE1 6IE1
9IG1
4
7
6 4
19 15
1
3 20 16
2
18 4
97 313
6 7
IJ 1J
5
3A 1E 1C
1A
1I
15
1C
1F
1K 3D
7B 1A
2 1 9
10
BK IF 1H
1K 1J 1E W± BY Y
G± O G
G
W± L
Y
Y
W± B
R± Y
W± G
G± W
W± LW± L
W± L W
W± B R± W
W± B
R
L±W P± B
G±L
R± W
R± W
BR± W
B±L
B±L
W±B
W± B
W±B W±B W±B
W±B W±B
R± W
R± W
R± WR± W
R± W R±B R±B
W
G± W
G± W W
P±L
W± L
G G
P±L
B±Y
W
R± Y R±L R
YVPower
Source
F9
FUSE BL OCK60A MAIN 100A AM1
120A ALT
W
R±Y
40A
IGSW
LO
HI
HI
LO
HEADLIGHT LH
HEADLIGHT RH
HEADLIGHT
RELAY
Fr om Connerring Light
Relay< 7±2> DI ODE10A DOME
7. 5A RADIO No. 2
LIGHT
CONTROL
DIMMER
OFF
TAIL
HEAD
LOW
HIGH
FLASH HU HF FL E D T H E L
C15
COMBINATI ON SW
BATTERY
C13
HIGH BEAM
I NDI CA TOR L I GHT
[COMB. METER]
To Door Lock Mot or and
Unlock Detection SW and
Doo r Open De t ect i on S W LH
<17±5><17±6>
To Door Lock Mot or and
Unlock Detection SW and
Doo r Open De t ect i on S W RH
< 17±6>
From Open Door War ning Light
From Per sonal Light< 6±2>
B4
BACKLE SW LH
I15
UNLOCK WARNI NG SW
[IGNITION SW] SEAT BELT WARNI NG
LI GHT[ COMB. MET ER]
5118
TAIL LIGHT
RELAY
To Thef t
Deter rent and
Do or L oc k ECU
< 17±3>
7. 5A PANEL15A TAIL
10A
GAUGE
3 12 2
13 4Y
BELT
H± LP B A CC TRLY I NTB I G
BKL KEY
12 12
9
To Theft Deterr ent and
Door Lock ECU< 17±3>
I15
IGNITION SW
I16
I NTEGRAT I ON REL AY
H
T
G± L
R±G
1 3
2
B±Y
G±O
1C
16DI ODE
1E
1
9
C1 2 , C1 4 AB
6
From Tens ion Reducer
Solenoid LH< 11±7>
Fr om Thef t Deter rent and
Door Loc k ECU< 17±2>
Fr om Day /Night Shift SW< 12±1>
Fr om Tilt and Power Teles copic
ECU< 11±1> Y
Y
B±L
W±B
5C 4C
CC 3 111 12 7
6428 510 GND
INTEGRATI ON RELAY
SEAT BELT
WARNING LIGHT
[COMB. METER]12
3456
10 11 12 13 17 18 19 20 21 12345 6789
14 15 16
17 18
1 2345 6789 10
23
22
21
20
19
15
14
13
12
11 16 C
A
B I16
C12
C1 4
Headlight and Light Auto Turn Off (
for USA ) Unlock and Seat Belt Warning
(
for USA )
(
Cont . ne xt pa ge )
2
1
1I 3
R± YR± Y
C6 C
21
Y
Right kic k panel
Under t he c ent er pillar LH Left k ick panel
IG1
8
15A
HEAD
RH
15A
HE AD
LH
W±B R
R
R
R
R
R 6Ba2
Ba1
11
5Ba2 Ba1
12 (
w/ ME MORY )
( w/ o MEMORY )
(
w/ Me mo r y )
( w/ o Memory )
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OVERALL ELECTRICAL WIRING DIAGRAM
1234
5 LEXUS SC300
1J
7 22 2 21J
81B2
4
1B
5
1B
4 1K
11
22 22
22
44
1I 1E
3 1
4 2 3
4
1 2 23
1
5
4
ACC
IG1
ST1
AM1 3
2
1 21 2 1
21
2
19 IE1 12 IE1 11 IE1 5IE1 6IE1
9IG1
4
7
6 4
15 19 21 1
3 16 20 22 2
18 497 313
6 7
IJ 8IG1 1J
5
3A 1E 1C
1A
1I
15
1C
1F
1K 3D
7B 1A
2 1 9
10
BK IF 1H
1K 1J 1E W± BY Y
G± O G
G
W± L
Y
Y
W±B
R
W±B W±B R±YW± G
G± W
W± LW± L
W± L W
W± B
R±W W± B
W± B
R
R
LG±B G±W
L±W P± B
G±L
R± W
R± W
BR± W
B±L
B± L
W± B
W± B
W±B W±B W±B W±B W±B
W± B W± B
R±W
R±W
R
W±B R±B R± W
R± W R±G
R
W
G± W
G± W R
R R
W
P±L W
G G
P±L
B±Y
W
R± Y R±L R
Y VPower
Source
F9
FUSE BL OCK60A MAIN
100A AM1
120A ALT
22W
R±Y
TH
15A
HEAD
LH±LWR
15A HEAD RH±LWR
15A HEAD RH±UPR 15 A HEA D L H± UP R
40A
IGSW
H3LH
H4 RH
H2 RH H1LH
HEADLIGHT
(
LO )
HEADLIGHT (
HI )
DIMMER
RE LA Y HEADLIGHT
RELAY
Fr om Connerring Light
Relay< 8±7> DI ODE10A DOME
7. 5A RADIO No. 2
LIGHT
CONTROL
DIMMER
OFF
TAI L
HE AD
LOW
HI GH
FLASH ED HL HU HF EL T H
C15
COMBINATI ON
SW
BATTERY
C13
HIGH BEAM
I NDI CA TOR L I GHT
[COMB. METER]
To Door Lock Mot or and
Unlock Detection SW and
Doo r Open De t ect i on S W LH
< 17±1>
To Door Lock Mot or and
Unlock Detection SW and
Doo r Open De t ect i on S W RH
< 17±1> From Open Door War ning Light
From Per sonal Light< 6±2>
B4
BACKLE SW LH
I15
UNLOCK WARNING SW
[IGNITION SW] SEAT BELT WARNI NG
LI GHT[ COMB. MET ER]
5118
TAIL LIGHT
RELAY
To Thef t
Deter rent and
Do or L oc k ECU
< 17±3>
7. 5A PANEL15A TAIL
10A
GAUGE
3 12 2
13 4Y
BELT
H± LP B A CC TA I L I NTB I G
BKL KEY
12 2
9
To Thef t Deter rent
and Door Loc k ECU
< 17±3>
I15
IGNITION SW
I16
I NTEGRAT I ON REL AY
DIM TOUT
HF
HU
Y± B
R±L
CHG± P KBY±G
B
From Alternator º Lº < 1±2>
From Park ing Br ake SW < 21±2>
1 3 2
B±Y
G± O
1C
16DI ODE
1E
1
9
C1 2 , C1 4 AB
6
From Tens ion Reducer
Solenoid LH< 11±7>
Fr om Thef t Deter rent and
Door Loc k ECU< 17±2>
Fr om Day /Night Shift SW< 12±1>
Fr om Tilt and Power Teles copic
ECU< 11±1> Y
Y
W±B
12C 11C 5C
CCC CC 4C2C 9 8 7 10 13 111 12 7
642 8 105 GND
I NTEGRATI ON REL AY
SEAT BELT
WARNING LIGHT
[COMB. METER]
10 11 12 13 17 18 19 20 21 12345 6789
14 15 16
17 18
1 2345 6789 10
23
22
21
20
19
15
14
13
12
11 16 C
A
B I16
C12
C1 4
Headlight (
for Canada ) Unlock and
Seat Belt Warning
(
for Canada )
(
Cont . ne xt pa ge )
2
1
3C 1C
13
Y
12345678910111213
18
17
IG
W±B
6Ba2Ba 1
11
5Ba2 Ba 1
12 (
w/ Memor y )
( w/o Memory )
B±L
( w/ Memor y )
( w/o Memory )
XX
Right kic k panel
Unlock the center
pillar LHLeft kic k
panel
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