Lexus SC300 / Lexus SC400. Service manual - part 189

Door Key Lock and Unlock Switch Circuit

CIRCUIT DESCRIPTION

The door key lock and unlock switch is built in the door key cylinder.
When the key is turned to the lock side, terminal 3 of the switch is grounded and when the key is turned
to the unlock side, terminal 1 of the switch is grounded.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

OK

OK

NG

NG

Check door key lock and unlock switch.

Check harness and connectors between ECU
and switch, switch and body ground 
(See page 

IN–27

).

Replace door key lock and unlock
switch.

1

2

Proceed to next circuit inspection shown on
matrix chart (See page 

BE–371

).

Repair or replace harness or
connector.

WIRING DIAGRAM

BE–386

–

BODY ELECTRICAL SYSTEM

Door Lock Control System

OK

NG

OK

NG

INSPECTION PROCEDURE

1

Check door key lock and unlock switch.

C

OK

P

1.

Remove the door trim and service hole cover.

2.

Disconnect the door ley lock and unlock switch con-
nector.

Check continuity between terminals 1, 2 and 3 of door
key lock and unlock switch is turned to the lock side, un-
lock side and not turned.

Replace door key lock and unlock switch.

2

Check harness and connectors between ECU ans switch, switch and body ground (See page

IN–27

).

Repair or replace harness or connector.

Proceed to next circuit inspection shown on ma-
trix chart (See page 

BE–371

).

–

BODY ELECTRICAL SYSTEM

Door Lock Control System

BE–387

OK

OK

NG

NG

Check key unlock warning switch.

Check harness and connectors between ECU and
key unlock warning switch, key unlock warning
switch and body ground (See page 

IN–27

).

Replace key unlock warning
switch.

1

2

Proceed to next circuit inspection shown on
matrix chart (See page 

BE–371

).

Repair or replace harness or
connector.

WIRING DIAGRAM

Key Unlock Warning Switch Circuit

CIRCUIT DESCRIPTION

The key unlock warning switch goes on when the ignition key is inserted in the key cylinder and goes
off when the ignition key is removed.
The ECU operates the key confinement prevention function while the key unlock warning switch is on.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

BE–388

–

BODY ELECTRICAL SYSTEM

Door Lock Control System

OK

NG

OK

NG

INSPECTION PROCEDURE

1

Check key unlock warning switch.

C

OK

P

Disconnect key unlock warning switch connector.

Check continuity between terminal 9 and 10 of key un-
lock warning switch connector, when the key is inserted
to the key cylinder or removed.

Replace key unlock warning switch.

2

Check harness and connectors between ECU and key unlock warning switch, key unlock warn-
ing switch and body ground (See page 

IN–27

).

Repair or replace harness or connector.

Proceed to next circuit inspection shown on ma-
trix chart (See page 

BE–371

).

–

BODY ELECTRICAL SYSTEM

Door Lock Control System

BE–389