Lexus SC300 / Lexus SC400. Manual - part 986

2

INTRODUCTION

This manual consists of the following 11 sections:

No.

Section

Description

A

INDEX

Index of the contents of this manual.

A

INTRODUCTION

Brief explanation of each section.

B

HOW TO USE
THIS MANUAL

Instructions on how to use this manual.

C

TROUBLE–
SHOOTING

Describes the basic inspection procedures for electrical circuits.

D

ABBREVIATIONS

Defines the abbreviations used in this manual.

E

GLOSSARY OF
TERMS AND
SYMBOLS

Defines the symbols and functions of major parts.

F

RELAY LOCATIONS

Shows position of the Electronic Control Unit, Relays, Relay Block, etc.
This section is closely related to the system circuit.

G

ELECTRICAL
WIRING ROUTING

Describes position of Parts Connectors, Splice points, Ground points, etc.
This section is closely related to the system circuit.

H

POWER SOURCE
(Current Flow Chart)

Describes power distribution from the power supply to various electrical
loads.

INDEX

Index of the system circuits.

I

SYSTEM CIRCUITS

Electrical circuits of each system are shown from the power supply through
ground points. Wiring connections and their positions are shown and
classified by code according to the connection method. (Refer to the
section, “How to use this manual”).
The “System Outline” and “Service Hints” useful for troubleshooting are also
contained in this section.

J

GROUND POINTS

Shows ground positions of all parts described in this manual.

K

OVERALL
WIRING DIAGRAM

Provides circuit diagrams showing the circuit connections.

108

LIGHT AUTO TURN OFF

1K

11

2

2

1D

8

IF

1J

1

1K

5

1B

2

2

1B

5

4

4

4

B

11

A

3

A

6

B

12

1D

10

6

4

2

4

7

3

1

2

4

3

3

13

6

1

3

1

IE1

6

10A
GAUGE

10A
DOME

R–Y

W

W–

B

R–

W

W–

B

W–

B

R–

G

G–

L

W

W–

L

W

W–

G

R–

Y

R–

Y

W–

L

R

G–

W

FROM POWER SOURCE SYSTEM (SEE PAGE 56)

BATTERY

FUSE BLOCK

INTEGRATION
RELAY

TAILLIGHT
RELAY

HEADLIGHT
RELAY

FR

O

M

C

O

R

N

E

R

IN

G

L

IG

H

T

R

EL

AY

TO

D

IM

M

E

R

S

W

LI

G

H

T

C

O

NT

RO

L

S

W

D

OOR

OP

E

N

DE

T

E

CT

IO

N

S

W

L

H

120

A

A

LT

100

A

A

M

1

60

A

M

A

IN

Q

Q

S

R

R

S

OFF

TAIL

HEAD

COMBINATION SW

F 9

C15

D1

0

I16

DIODE

3

2

5

1

B

A

R–

Y

7

A

4

B

10

B

13

A

5

R–Y

(CANADA)

(USA)

(USA)

(CANADA)

2

I 5

1

10

6

109

WITH THE IGNITION SW TURNED ON, THE CURRENT FLOWS TO TERMINAL 7 OF THE INTEGRATION RELAY THROUGH GAUGE
FUSE. VOLTAGE IS APPLIED AT ALL TIMES TO TERMINAL (A)4 (USA), (B)11 (CANADA) OF THE INTEGRATION RELAY THROUGH THE
TAILLIGHT RELAY COIL, AND TO TERMINAL (A)5 (USA), (B)12 (CANADA) THROUGH THE HEADLIGHT RELAY COIL.

1. NORMAL LIGHTING OPERATION

TURN TAILLIGHT ON

WITH LIGHT CONTROL SW TURNED TO TAILLIGHT POSITION, A SIGNAL IS INPUT INTO TERMINAL (A)3 (USA), (B)10 (CANADA) OF
THE INTEGRATION RELAY. DUE TO THIS SIGNAL, THE CURRENT FLOWING TO TERMINAL (A)4 (USA), (B)11 (CANADA) OF THE RELAY
FLOWS TO TERMINAL (A)3 (USA), (B)10 (CANADA) 

→

 TERMINAL 3 OF THE LIGHT CONTROL SW 

→

TERMINAL 4 

→

 TO GROUND AND

TAILLIGHT RELAY CAUSES TAILLIGHT TO TURN ON.

TURN HEADLIGHT ON

WITH LIGHT CONTROL SW TURNED TO HEADLIGHT POSITION, A SIGNAL IS INPUT INTO TERMINALS (A)3 (USA). (B)10 (CANADA)
AND (A)6 (USA), (B)13 (CANADA) OF THE INTEGRATION RELAY. DUE TO THIS SIGNAL, THE CURRENT FLOWING TO TERMINAL (A)5
(USA), (B)12 (CANADA) OF THE RELAY FLOWS TO TERMINAL (A)6 (USA), (B)13 (CANADA) 

→

 TERMINAL 13 OF THE LIGHT CONTROL

SW 

→

 TERMINAL 4 

→

 TO GROUND IN THE HEADLIGHT CIRCUIT, AND CAUSES TAILLIGHT AND HEADLIGHT RELAY TO TURN ON. THE

TAILLIGHT CIRCUIT IS SAME AS ABOVE.

2. LIGHT AUTO TURN OFF OPERATION

WITH LIGHTS ON AND IGNITION SW TURNED OFF (INPUT SIGNAL GOES TO TERMINAL 7 OF THE RELAY), WHEN DOOR ON DRIVER’S
SIDE IS OPENED (INPUT SIGNAL GOES TO TERMINAL 6 OF THE RELAY), THE RELAY OPERATES AND THE CURRENT IS CUT OFF
WHICH FLOWS FROM TERMINAL (A)4 (USA), (B)11 (CANADA) OF THE RELAY TO TERMINAL (A)3 (USA), (B)10 (CANADA) IN TAILLIGHT
CIRCUIT AND FROM TERMINAL (A)5 (USA), (B)12 (CANADA) TO TERMINAL (A)6 (USA), (B)13 (CANADA) IN HEADLIGHT CIRCUIT.

AS A RESULT, ALL LIGHTS ARE TURNED OFF AUTOMATICALLY.

HEADLIGHT RELAY

1–2 : CLOSED WITH LIGHT CONTROL SW AT HEAD POSITION OR DIMMER SW AT FLASH POSITION

TAILLIGHT RELAY

5–3 : CLOSED WITH LIGHT CONTROL SW AT TAIL OR HEAD POSITION

I16

(A)(B)  INTEGRATION RELAY

7–GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
6–GROUND : CONTINUITY WITH DOOR LH OPEN
(A)4, (B)11–GROUND: ALWAYS APPROX. 12 VOLTS
(A)5, (B)12–GROUND: ALWAYS APPROX. 12 VOLTS
(A)6, (B)13–GROUND: CONTINUITY WITH LIGHT CONTROL SW AT HEAD POSITION
(A)3, (B)10–GROUND: CONTINUITY WITH LIGHT CONTROL SW AT TAIL OR HEAD POSITION

D10

  DOOR LOCK MOTOR, DOOR UNLOCK DETECTION SW AND DOOR OPEN DETECTION SW LH

3–6 : CLOSED WITH DOOR LH OPEN

: PARTS LOCATION

CODE

SEE PAGE

CODE

SEE PAGE

CODE

SEE PAGE

C15

28

F 9

26

I16

B

29 (CANADA)

D10

30

I16

A

29 (USA)

: RELAY BLOCKS

CODE

SEE PAGE

RELAY BLOCKS (RELAY BLOCK LOCATION)

2

19

ENGINE COMPARTMENT LEFT

4

23

LEFT KICK PANEL (J/B NO.1 LEFT)

: JUNCTION BLOCK AND WIRE HARNESS CONNECTOR

CODE

SEE PAGE

JUNCTION BLOCK AND WIRE HARNESS (CONNECTOR LOCATION)

1B

20

ENGINE ROOM MAIN WIRE

1D

20

FRONT DOOR LH WIRE

1J

20

COWL WIRE

1K

20

COWL WIRE

: CONNECTOR JOINING WIRE HARNESS AND WIRE HARNESS

CODE

SEE PAGE

JOINING WIRE HARNESS AND WIRE HARNESS (CONNECTOR LOCATION)

IE1

36

ENGINE WIRE AND COWL WIRE (R/B NO.4)

SYSTEM OUTLINE

SERVICE HINTS

110

LIGHT AUTO TURN OFF

: GROUND POINTS

CODE

SEE PAGE

GROUND POINTS LOCATION

IF

36

LEFT KICK PANEL

: SPLICE POINTS

CODE

SEE PAGE

WIRE HARNESS WITH SPLICE POINTS

CODE

SEE PAGE

WIRE HARNESS WITH SPLICE POINTS

I 5

38

COWL WIRE