Lexus SC300 / Lexus SC400. Manual - part 177

WIRING DIAGRAM

CIRCUIT INSPECTION

ECU Power Source Circuit

CIRCUIT DESCRIPTION

This circuit provides power for ECU operation and is also the power source for the slide position sensor.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Check DOME fuse.

NG

OK

NG

NG

OK

OK

Check for short in all the harness
and components connected to
DOME fuse.  (See attached wir-
ing diagram).

Check voltage between terminals SYSB and
GND of ECU connector.

Proceed to next circuit inspection
shown on matrix chart.  

(See page 

BE–319

).

Check continuity between terminal GND of 
ECU connector and body ground.

Repair or replace harness or 
connector.

Check and repair harness or connector 
between ECU and battery.

BE–324

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

OK

NG

NG

OK

OK

NG

INSPECTION PROCEDURE

1

Check DOME fuse.

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

2

Check voltage between terminals SYSB and GND of ECU connector.

C

OK

P

Remove ECU with connectors still connected.

Measure voltage between terminals SYSB and GND of
ECU connector.

Voltage:

10 –14 V

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

BE–319

).

3

Check continuity between terminal GND of ECU connector and body ground.

C

OK

Measure resistance between terminal GND of ECU con-
nector and body ground.

Resistance:

1 

 or less

Repair or replace harness or connector.

Check and repair harness or connector between
ECU and battery.

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

BE–325

Check DOOR fuse.

NG

OK

NG

OK

NG

OK

Check for short in all the harness
and components connected to
the DOOR fuse (See attached
wiring diagram). *

1

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

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

BE–319

).

Check continuity between terminal GND of
ECU connector and body ground.

Repair or replace harness of
connector.

Check and repair harness or connector
between ECU and battery.

*

1

The power source is supplied to the actuator
(Slide motor) through the passenger’s seat
ECU accordingly, if a short circuit of the W/H
or actuator occurs in the actuator circuit, the
DOOR fuse may become open, so also in-
spect the actuator. (Slide motor circuit on

page 

BE–328

).

WIRING DIAGRAM

Slide Motor Power Source Circuit

CIRCUIT DESCRIPTION

This is the power source for slide motor.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

BE–326

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

OK

NG

NG

OK

OK

NG

INSPECTION PROCEDURE

1

Check DOOR fuse.

Check for short in all the harness components con-
nected to the DOOR fuse and repair them (See attached
wiring diagram). *1

2

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

C

OK

P

Remove passenger’s seat ECU with connectors still
connected.

Measure voltage between terminals +B and GND of
ECU connector.

Voltage:

10 – 14 V

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

BE–319

).

3

Check continuity between terminal GND of ECU connector and body ground.

C

OK

Measure resistance between terminal GND of ECU and
body ground.

Resistance:

1 

 or less

Repair or replace harness or connector.

Check and repair harness or connector between
ECU and battery.

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

BE–327