Lexus SC300 / Lexus SC400. Manual - part 173

WIRING DIAGRAM

Check harness and connector between
ECU and tilt & telescopic ECU (See page

IN–27

).

NG

NG

OK

OK

Check return operation of tilt and
telescopic ECU, and mirror ECU.

Repair or replace harness or
connector.

Check and replace tilt &
telescopic ECU.

Proceed to next circuit inspection shown on

matrix chart (See page 

BE–276

).

Serial Communication Circuit

CIRCUIT DESCRIPTION

Memory and return command signals and mutual commu-
nication during return operation pass between the ECU and
the tilt & telescopic ECU in the from of serial data communica-
tion. Signals activating memory and return operation are sent
from the tilt & telescopic ECU to the ECU and mirror ECU.
When the ECU receives a memory signals, its position is
memorized, and when a return signal is received, the position
is returned to the memorized position.

During return operation, tilt & telescopic ECU and ECU continue mutual communication constantly, and if a mal-
function should occur in the communication wire, the tilt & telescopic ECU stops signal output to the ECU and
stops return operation. However, the tilt & telescopic ECU continues return operation. Even with power return
stopped, manual switch operation of the power seat is possible. The mirror ECU receives activation signals only
and is not involved in reciprocal communication during return operation, so even when a reply signal from the
ECU to the tilt & telescopic ECU is abnormal and the power seat stops return operation, the mirror ECU contin-
ues return operation.

DIAGNOSTIC CHART

DIAGNOSTIC CHART

BE–306

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Driver’s Seat)

OK

NG

OK

NG

INSPECTION PROCEDURE

1

Check for open and short in harness and connector between ECU and tilt & telescopic ECU (See

page 

IN–27

).

Hint

Depending on the differences that exist for return opera-
tion or non–return operation of each system, the prob-
lems is the harness and connector shown in the table
below may be considered.

Trouble area

Tilt &

Telescopic

Mirror Seat

Open

Short

Open

Open or Short

Repair or replace harness or connector.

2

Check return operation by tilt & telescopic ECU, and mirror ECU.

Check that return operation is normal for tilt, telescopic and mirror functions.

C

Check and replace tilt & Telescopic ECU.

Proceed to next circuit inspection shown on 

matrix chart (See page 

BE–276

).

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Driver’s Seat)

BE–307

POWER SEAT CONTROL SYSTEM
(Passenger’s seat)

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)

BE–309

DESCRIPTION

In walk–in operation, when the passenger’s seat back is reclined fully forward, this is detected by the limit switch
and the seat slides forward electronically. In return operation, when the seat back is pulled upright the seat slides
back electronically.

1). Walk–in 

Operation

a).  When the initial seat position is 100 mm (3.94 in.) or more behind the the foremost position, the seat

will slide forward 100 mm (3.94 in.) in one slide operation.

b).  When the initial seat position is less than 100 mm (3.94 in.) away from the foremost position, the seat

only slides forward to the foremost position.

c).  If the seatback is raised approximately 10

°

 during walk–in operation, slide operation stops and will

not resume even if the seatback is fully reclined again.

d).  If the seatback is pulled upright to a lock position during slide operation, the seat slide direction is re-

versed (becomes return operation).

e).  Walk–in operation will not occur when the slide manual switch is operated or when the tongue of the

passenger ’s seat belt is inserted in the buckle.

2). Return 

Operation

a).  If the seatback is reclined a minimum of 10

°

 during return operation, the slide operation stops and will

not resume even if the seatback is pulled back to lock position.

b).  If the seatback is reclined forward during return operation, the seat slide direction changes to forward

movement (walk–in operation).

c).  When the slide manual switch is operated or the slide distance exceeds 150 mm (5.91 in.), return op-

eration stops.

BE–310

–

BODY ELECTRICAL SYSTEM

Power Seat Control System (Passenger’s Seat)