Lexus ES300 (1997 year). Service manual - part 399

DI0FT–01

N21495
N21496
N21464

I00703

Instrument Panel Junction Block

 AM1 Fuse

 STOP Fuse

 GAUGE Fuse

 ECU–IG Fuse

Engine Room Junction Block

 ECU–B Fuse

Front Vertical Motor

Slide Motor

Rear Vertical Motor

Seat Position Control ECU

Power Seat Control Switch

Seat Memory Switch

Reclining Motor

–

DIAGNOSTICS

POWER SEAT CONTROL SYSTEM

DI–373

525

1997 LEXUS ES300   (RM511U)

PARTS LOCATION

DI0FV–01

DI–374

–

DIAGNOSTICS

POWER SEAT CONTROL SYSTEM

526

1997 LEXUS ES300   (RM511U)

PROBLEM SYMPTOMS TABLE

Perform troubleshooting of the circuits for the applicable problem symptom in the order given in the chart
below. Proceed to the page located for each circuit.
HINT:

If the instruction ”Proceed to next circuit inspection shown on matrix chart” is given in the flow chart
for each circuit, proceed to the circuit with the next highest number in the table to continue the check.

If the trouble still reappears even though there are no abnormalities in any of the other circuits, then
check and replace the Seat Position Control ECU as the last step.

Symptom

Suspect Area

See page

Both manual & return functions do not operate(All functions).

1. +B power source circuit

2. Power seat control switch circuit

3. Motor circuit 

4. Power seat control ECU

DI–375

DI–392

DI–379

IN–27

Both manual & return functions do not operate(One function only).

1. Motor circuit 

2. Power seat control ECU

DI–379

IN–27

One or all functions do not operate for manual operation only.

1. Power seat control switch circuit

2. Power seat control ECU

DI–392

IN–27

Memory function does not operate.

1. Power seat memory switch circuit

2. Ignition switch circuit 

3. Park/neutral position switch circuit

4. Power seat control ECU

DI–394

DI–390

DI–388

IN–27

Return operation does not stop when brake pedal is depressed.

1. Stop light switch circuit

2. Power seat control ECU

DI–386

IN–27

Only return function does not operate or operates a little, then

stops (All return functions).

1. Power seat memory switch circuit 

2.ECU power source circuit 

3.Position sensor power source circuit

4.Power seat control ECU

DI–394

DI–377

DI–382

IN–27

Only return function does not operate or operates a little, then

stops (Only one return function).

1. Position sensor circuit

2.Power seat control ECU

DI–384

IN–27

DI0FY–01

N21259

BR

Battery

POWER

Instrument Panel J/B

ALT

Seat Position Control ECU

FL MAIN

+B

SGND

GND

L–W

AM1

F/L

J37

Instrument Panel J/B

L–W

L–W

BR

W–B

W–B

IF2

F8

F6

B–R

2

7

1B

1K

1B

1D

3

8

7

9

8

7

8

11

A

A

S14

S15

BS2

S14

BS2

BS2

B–R

B–G

BN

IH

4

2

1

N21258

LOCK

(–)

+B

8

(+)

GND

Seat Position Control ECU

Connect

7

–

DIAGNOSTICS

POWER SEAT CONTROL SYSTEM

DI–375

527

1997 LEXUS ES300   (RM511U)

CIRCUIT INSPECTION

+B Power Source Circuit

CIRCUIT DESCRIPTION

This is the power source for motors such as the slide motor, reclining motor, front vertical motor and rear
vertical motor.

WIRING DIAGRAM

INSPECTION PROCEDURE

1

Check voltage between terminals +B and GND of Seat Position Control ECU con-
nector.

PREPARATION:
Remove Seat Position Control ECU with connectors still con-
nected.
CHECK:
Measure voltage between terminals +B and GND of Seat Posi-
tion Control ECU connector.
OK:
Voltage: 10 – 14 V

OK

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

DI–374

).

N21251

GND

Seat Position Control ECU

Disconnect

7

DI–376

–

DIAGNOSTICS

POWER SEAT CONTROL SYSTEM

528

1997 LEXUS ES300   (RM511U)

NG

2

Check continuity between terminals GND of Seat Position Control ECU connec-
tor and body ground.

CHECK:
Measure resistance between terminals GND of Seat Position
Control ECU connector and body ground.
OK:
Resistance: Continuity (below 1 

Ω

)

NG

Repair or replace harness or connector.

OK

3

Check AM1 fuse and POWER fuse.

NG

Check for short in all the harness and compo-
nents connected to the AM1 and POWER fuse,
and repair them (See attached wiring diagram).

OK

Check and repair harness or connector be-
tween Seat Position Control ECU and battery.