Lexus SC300 / Lexus SC400. Service manual - part 197

OK

NG

NG

OK

OK

NG

OK

NG

INSPECTION PROCEDURE

1

Check DOME fuse.

Check for short in all the harness and components con-
nected to DOME fuse (See attached wiring diagram).

2

Check voltage between terminals +B and E of ECU connector.

C

OK

P

1.

Remove the rear seat and RH quarter trim panel.

2.

Remove the ECU.

Measure voltage between terminals +B and E of ECU
connector, when wireless door lock main switch is on
and off.

Wireless door lock main switch

ON

OFF

Voltage

10 – 14 V
Below 1 V

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

BE–454

).

3

Check for open in harness and connector between terminal E of ECU and body ground 

(See page 

IN–27

).

Repair or replace harness or connector.

4

Check wireless door lock main switch.

C

OK

P

1.

Remove the instrument lower finish panel.

2.

Remove wireless door lock main switch.

3.

Disconnect the connector.

Measure resistance between terminals of wireless door
lock main switch connector, when main switch is on and
off.

Wireless door lock main switch

ON

OFF

Resistance

Continuity

1M  or higher

Replace wireless door lock main switch.

Check and repair harness and connector between
ECU and main switch, main switch and battery.

–

BODY ELECTRICAL SYSTEM

Wireless Door Lock Control System

BE–461

WIRING DIAGRAM

Door Unlock Detection Switch Circuit

CIRCUIT DESCRIPTION

The door unlock detection switch is built into the door lock motor assembly. The switch is OFF when the door
lock knob is in Lock position, and is ON when the knob is in Unlock position.
Furthermore, the door unlock detection switch circuit has terminal + B connected inside the theft deterrent ECU,
when the door unlock detection switch is OFF, battery positive voltage is applied to the terminal of the door un-
lock detection switch circuit of the wireless door lock ECU.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

NG

OK

Proceed to next circuit inspec-
tion shown on matrix chart (See
page 

BE–454

).

Check voltage between terminals LSWD1
LSWP and LSWD2 of ECU connector and
body ground.

Check and repair harness and connector
between ECU and door unlock detection
switch.

1

BE–462

–

BODY ELECTRICAL SYSTEM

Wireless Door Lock Control System

NG

OK

INSPECTION PROCEDURE

1

Check voltage between terminals LSWD1, LSWP and LSWD2 of ECU connector and body
ground.

C

OK

P

1.

Remove the rear seat and RH quarter trim panel.

2.

Remove the ECU.

3.

Turn ignition switch on.

Measure voltage between terminals LSWD1, LSWP
and LSWD2 of ECU connector and body ground, when
the respective door lock knob involved is pushed to the
lock side.

Voltage:

8 – 10 V

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

BE–454

).

Check and repair harness and connector between ECU and door unlock detection switch.

–

BODY ELECTRICAL SYSTEM

Wireless Door Lock Control System

BE–463

WIRING DIAGRAM

Door Key Lock and Unlock Switch Circuit (Unlock Side)

CIRCUIT DESCRIPTION

The door key lock and unlock switch is built into the door key cylinder. When the key is turned to the lock side,
the lock terminal of the switch is grounded, and when the key is turned to the unlock side the unlock terminal
is grounded.
Furthermore, the door key lock and unlock switch circuit has terminal +B connected inside the theft deterrent
and door lock ECU, when neither the lock or unlock terminal of the door key lock and unlock switch are grounded,
battery positive voltage is applied to the door key lock and unlock switch circuit of the wireless door lock ECU.
(Tr inside the ECU coming ON causes the wireless door lock ECU to output a signal to unlock all the doors.)

DIAGNOSTIC CHART

DIAGNOSTIC CHART

NG

OK

Proceed to next circuit inspec-
tion shown on matrix chart (See
page 

BE–454

).

Check voltage between terminal UL1 of
ECU connector and ground.

Check and repair harness and connector
between ECU and key door key lock and
unlock switch.

1

BE–464

–

BODY ELECTRICAL SYSTEM

Wireless Door Lock Control System