Lexus LS400 (2000 year). Service manual — part 53

Z14885

From Back Side

BE–40

–

BODY ELECTRICAL

HEADLIGHT AND TAILLIGHT SYSTEM

1903

(b)

Connect the wire harness side connector to the light con-
trol switch and inspect the connector from the back side,
as shown.

Light Control Switch Circuit
See page

DI–678

Fog Light Switch Circuit

Tester connection

Condition

Specified condition

12 – Ground

Light control switch HEAD and dimmer switch

position HI or FLASH

No voltage

12 – Ground

Light control switch HEAD and dimmer switch

position LO

Battery positive voltage

Dimmer Switch Circuit

Tester connection

Condition

Specified condition

8 – Ground

Light control switch HEAD and dimmer switch

LOW

No voltage

8 – Ground

Headlight dimmer switch FLASH or Light control

switch HEAD and dimmer switch HIGH

Battery positive voltage

18 – Ground

Light control switch HEAD and dimmer switch

HIGH or FLASH

No voltage

18 – Ground

Light control switch HEAD and dimmer switch

LOW

Battery positive voltage

Turn Signal Switch Circuit

Tester connection

Condition

Specified condition

1 – Ground

Ignition switch ON and turn signal switch position

Left

Battery positive voltage

3 – Ground

Ignition switch ON and turn signal switch position

Right

Battery positive voltage

If the circuit is not as specified, inspect the circuits connected
to other parts.

I03478

Wire Harness Side

Light Control Switch
Connector ”A”

Daytime Running Light Relay
Connector ”B”

Z14887

From Back Side

–

BODY ELECTRICAL

HEADLIGHT AND TAILLIGHT SYSTEM

BE–41

1904

7.

CANADA:
INSPECT SWITCH CIRCUIT

(a)

Disconnect the light control switch and daytime running
light relay connectors, and inspect the each connector on
the wire harness side, as shown.

Light Control Switch Circuit

Tester connection

Condition

Specified condition

A16 – Ground

Constant

Continuity

Dimmer Switch Circuit

Tester connection

Condition

Specified condition

A17 – Ground

Constant

Continuity

A8 – B8

Constant

Continuity

A9 – B2

Constant

Continuity

If the circuit is not as specified, inspect the wire harness.

(b)

Connect the wire harness side connector to the light con-
trol switch and inspect the connector from the back side,
as shown.

Fog Light Switch Circuit

Tester connection

Condition

Specified condition

11 – Ground

Light control switch OFF

No voltage

11 – Ground

Light control switch TAIL, HEAD or AUTO and

Fog light switch ON

Battery positive voltage

12 – Ground

Light control switch OFF

No voltage

12 – Ground

Light control switch TAIL, HEAD or AUTO

Battery positive voltage

Z09181

3

1

2

4

1

4

2

3

Z14984

Z08885

BE–42

–

BODY ELECTRICAL

HEADLIGHT AND TAILLIGHT SYSTEM

1905

Turn Signal Switch Circuit

Tester connection

Condition

Specified condition

2 – Ground

Constant

Continuity

1 – Ground

Ignition switch ON and Turn signal switch

position Left

No voltage

3 – Ground

Ignition switch ON and Turn signal switch

position Right

Battery positive voltage

If the circuit is not as specified, inspect the circuits connected
to other parts.

8.

INSPECT HEADLIGHT CONTROL RELAY CONTINU-
ITY

Condition

Tester connection

Specified condition

Constant

3 – 4

Continuity

Apply B+ between

terminals 3 and 4.

1 – 2

Continuity

If continuity is not as specified, replace the relay.
9.

INSPECT HEADLIGHT CONTROL RELAY CIRCUIT
(See page

BE–23

)

10.

INSPECT TAILLIGHT CONTROL RELAY CONTINUITY

Condition

Tester connection

Specified condition

Constant

1 – 2

Continuity

Apply B+ between

terminals 1 and 2.

3 – 4

Continuity

If continuity is not as specified, replace the relay.
11.

INSPECT TAILLIGHT CONTROL RELAY CIRCUIT
(See page

BE–23

)

12.

INSPECT HEADLIGHT DIMMER AND DAYTIME RUN-
NING LIGHT NO.2 RELAY CONTINUITY

Condition

Tester connection

Specified condition

Constant

1 – 4

2 – 4

Continuity

Apply B+ between

terminals 2 and 4.

3 – 4

Continuity

If continuity is not as specified, replace the relay.
13.

INSPECT HEADLIGHT DIMMER RELAY CIRCUIT
(See page

BE–23

)

N21564

Wire Harness Side

1

2

3

4

5 6

7

8

9 10

h–10–1–A

–

BODY ELECTRICAL

HEADLIGHT AND TAILLIGHT SYSTEM

BE–43

1906

14.

INSPECT DAYTIME RUNNING LIGHT RELAY CIRCUIT

Disconnect the connector from the relay and inspect the con-
nector on the wire harness side.

Tester connection

Condition

Specified condition

2 – Ground

Light control switch position OFF or TAIL

No continuity

2 – Ground

Light control switch position HEAD

Continuity

4 – Ground

Parking brake switch position OFF

(Parking brake lever released)

No continuity

4 – Ground

Parking brake switch position ON

(Parking brake lever pulled up)

Continuity

6 – Ground

Constant

Continuity

8 – Ground

Headlight dimmer switch position

Low beam

No continuity

8 – Ground

Headlight dimmer switch position

High beam or Flash

Continuity

10 – Ground

Brake fluid level warning switch position OFF

No continuity

10 – Ground

Brake fluid level warning switch position ON

Continuity

1 – Ground

Ignition switch position LOCK or ACC

No voltage

1 – Ground

Ignition switch position ON or START

Battery positive voltage

5 – Ground

Engine Stop

No voltage

5 – Ground

Engine Running

Battery positive voltage

7 – Ground

Constant

Battery positive voltage

9 – Ground

Constant

Battery positive voltage

If circuit is as specified, try replacing the relay with a new one.
If circuit is not as specified, inspect the circuits connected to oth-
er parts.