Lexus SC300 / Lexus SC400. Manual - part 178

WIRING DIAGRAM

Slide Motor Circuit

CIRCUIT DESCRIPTION

The passenger’s seat ECU control the slide motor.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Check slide motor.

NG

NG

OK

OK

Replace motor.

Repair or replace harness or
connector.

Check harness and connector between

ECU and motor (See page 

IN–27

).

Proceed to next circuit inspection shown

on matrix chart (See page 

BE–319

).

BE–328

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

OK

NG

OK

NG

INSPECTION PROCEDURE

1

Check Slide Motor.

C

OK

P

(1) Remove Seat

(2) Disconnect slide motor connector.

Check seat movement when battery voltage is applied
to slide motor.

Connect positive 

 (negative 



 ) terminal to terminal 1

of slide motor connector and negative 



 (positive 

 )

terminal to terminal 2.

Terminal

Movement

Forward

Back

1

2

Replace motor.

2

Check for open and short in harness and connector between ECU and motor (See page 

IN–27

).

Repair or replace harness or connector.

Proceed to next circuit inspection shown on ma-

trix chart (See page 

BE–319

).

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

BE–329

WIRING DIAGRAM

Position Sensor Circuit

CIRCUIT DESCRIPTION

The position sensor senses movement of the seat and send
pulse signals to the ECU. The position sensor sends pulses
to the ECU in proportion to the amount of seat movement, as
shown in the diagram on the left.
If a malfunction occurs in a position sensor and a sensor sig-
nal is not input to the ECU even when the motor operates, the
ECU prohibits return operation.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Inspect the circuit which is malfunctioning.

Position sensor check.

OK

NG

OK

OK

NG

NG

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

BE–319

)

Replace position sensor.

Check position sensor.

Check harness and connectors between

ECU and position sensor (See page 

IN–27

).

Repair or replace harness or
connector.

Check and replace ECU.

BE–330

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

INSPECTION PROCEDURE

1

Position Sensor Check.

C

Hint

P

(1) Remove the passenger’s seat.

(2) Remove the bolts for seat rail and lift the seat cush-

ion up a little.

Notice:   If the seat cushion is lifted too high, the har-
ness will be pulled and the clamp may come loose.

(3) Remove the ECU with the connector attached from

where it is installed to the underside of the seat
cushion.

Position sensor check

(1) Connect terminal CHK of the ECU to body ground

to put the ECU into check mode.

(2) Measure voltage between terminal DOUT of ECU

and body ground.

Use an analog type meter.

(3) Check that the “ready” code is output as shown in

the illustration.

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

BE–331