Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Power Seat Position is not Memorized

DESCRIPTION

The main body ECU (multiplex network body ECU) receives seat memory switch LH signals from the outer mirror control ECU assembly via CAN communication. If the SET switch is being pressed when one of the M1, M2 or M3 switches is pressed, or if one of the M1, M2 or M3 switches is pressed within 3 seconds of pressing the SET switch, the main body ECU (multiplex network body ECU) sends a memory request signal to the position control ECU and switch assembly LH. After receiving the request signal, the position control ECU and switch assembly LH memorizes the location data of each motor.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

PROCEDURE

1.	CHECK FRONT POWER SEAT CONTROL OPERATION

(a) Check that each function of the power seat operates normally by using the position control ECU and switch assembly LH.

Click here

OK:

Each function of the power seat operates normally using the position control ECU and switch assembly LH.

NG

GO TO PROBLEM SYMPTOMS TABLE

OK

2.	READ VALUE USING TECHSTREAM (SEAT MEMORY SWITCH LH)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Mirror L / Data List.

(e) Read the Data List according to the display on the Techstream.

Body Electrical > Mirror L > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Seat Memory Switch1	M1 switch	ON or OFF	ON: M1 switch on OFF: M1 switch off	-
Seat Memory Switch2	M2 switch	ON or OFF	ON: M2 switch on OFF: M2 switch off	-
Seat Memory Switch3	M3 switch	ON or OFF	ON: M3 switch on OFF: M3 switch off	-
Seat Memory Set SW	SET switch	ON or OFF	ON: SET switch on OFF: SET switch off	-

Body Electrical > Mirror L > Data List

Tester Display
Seat Memory Switch1
Seat Memory Switch2
Seat Memory Switch3
Seat Memory Set SW

OK:

On the Techstream screen, ON or OFF is displayed accordingly.

NG

GO TO STEP 8

OK

3.	PERFORM ACTIVE TEST USING TECHSTREAM (BUZZER)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Driver Seat / Active Test.

(e) Perform the Active Test according to the display on the Techstream.

Body Electrical > Driver Seat > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
Buzzer	Buzzer operation	OFF/ON	-

Body Electrical > Driver Seat > Active Test

Tester Display
Buzzer

OK:

Buzzer sounds normally.

NG

REPLACE POSITION CONTROL ECU AND SWITCH ASSEMBLY LH

OK

4.	REPLACE OUTER MIRROR CONTROL ECU ASSEMBLY (DRIVER DOOR)

(a) Replace the outer mirror control ECU assembly (driver door) with a new or known good one.

Click here

NEXT

5.	CHECK SEAT POSITION MEMORY AND RESTORING FUNCTION

(a) Check the seat position memory and restoring functions.

Click here

OK:

Seat position memory and restoring functions operate normally.

OK

END (OUTER MIRROR CONTROL ECU ASSEMBLY (DRIVER DOOR) WAS DEFECTIVE)

NG

6.	REPLACE POSITION CONTROL ECU AND SWITCH ASSEMBLY LH

(a) Replace the position control ECU and switch assembly LH with a new or known good one.

Click here

NEXT

7.	CHECK SEAT POSITION MEMORY AND RESTORING FUNCTION

(a) Check the seat position memory and restoring functions.

Click here

OK:

Seat position memory and restoring functions operate normally.

OK

END (POSITION CONTROL ECU AND SWITCH ASSEMBLY LH WAS DEFECTIVE)

NG

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

8.	INSPECT SEAT MEMORY SWITCH LH

(a) Remove the seat memory switch LH.

Click here

(b) Inspect the seat memory switch LH.

Click here

NG

REPLACE SEAT MEMORY SWITCH LH

OK

9.	CHECK HARNESS AND CONNECTOR (OUTER MIRROR CONTROL ECU ASSEMBLY (DRIVER DOOR) - SEAT MEMORY SWITCH LH - BODY GROUND)

(a) Disconnect the N4 outer mirror control ECU assembly (driver door) connector.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
N4-1 (MM) - N5-2 (MMRY)	Always	Below 1 Ω
N4-1 (MM) or N5-2 (MMRY) - Body ground	Always	10 kΩ or higher
N4-2 (M1) - N5-8 (1)	Always	Below 1 Ω
N4-2 (M1) or N5-8 (1) - Body ground	Always	10 kΩ or higher
N4-3 (M2) - N5-6 (2)	Always	Below 1 Ω
N4-3 (M2) or N5-6 (2) - Body ground	Always	10 kΩ or higher
N4-4 (M3) - N5-3 (3)	Always	Below 1 Ω
N4-4 (M3) or N5-3 (3) - Body ground	Always	10 kΩ or higher
N4-7 (GND) - Body ground	Always	Below 1 Ω
N5-1 (E) - Body ground	Always	Below 1 Ω

OK

REPLACE OUTER MIRROR CONTROL ECU ASSEMBLY (DRIVER DOOR)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR