Lexus SC300 / Lexus SC400. Service manual - part 168

OK

NG

NG

OK

OK

NG

INSPECTION PROCEDURE

1

Check DOOR fuse.

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

2

Check voltage between terminals +B, +B2 and GND of ECU connector.

C

OK

P

Remove ECU with connectors still connected.

Measure voltage between terminals +B, +B2 and GND
of ECU connector.

Voltage:

10 – 14 V

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

BE–276

.)

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 (Driver’s Seat)

BE–285

WIRING DIAGRAM

ECU Power Source Circuit

CIRCUIT DESCRIPTION

This circuit provides power for ECU operation and is also the power source for the sensors.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Check DOME fuse.

NG

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

OK

Check voltage between terminals SYSB
and SGND of ECU connector.

Proceed to next circuit inspection
shown on matrix chart 

(See page 

BE–276

).

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

OK

NG

OK

NG

Replace or repair harness or
connector.

Check and repair harness or connector
between ECU and battery.

BE–286

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Driver’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 the DOME fuse (See attached wiring diagram).

2

Check voltage between terminals SYSB and SGND of ECU connector.

C

OK

P

Remove ECU with connectors still connected.

Measure voltage between terminals SYSB and SGND
of ECU connector.

Voltage:

10 – 14 V

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

BE–276

).

3

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

C

OK

Measure resistance between terminal SGND of ECU
connector 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 (Driver’s Seat)

BE–287

WIRING DIAGRAM

Motor Circuit

CIRCUIT DESCRIPTION

The driver’s seat ECU controls the 4 motors for slide, front vertical, rear vertical and reclining.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Inspect the circuit of the motor which is malfunctioning.

Check motor.

NG

Replace motor.

OK

Check harness and connector between

ECU and motor (See page 

IN–27

).

NG

OK

Repair or replace harness or
connector.

Proceed to next circuit inspection shown

on matrix chart (See page 

BE–276

).

BE–288

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Driver’s Seat)