Lexus RX (RX 350L, RX450h) 2016-2026 Repair Manual: Power Seat does not Return to Memorized Position

DESCRIPTION

When the M1, M2 or M3 switch of the seat memory switch LH is pressed, the outer mirror control ECU assembly sends a switch signal to the main body ECU (multiplex network body ECU) via CAN communication. Then, the main body ECU (multiplex network body ECU) sends a recall request signal to the position control ECU and switch assembly LH. The position control ECU and switch assembly LH operates each motor to move the seat to the memorized position.

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.	CHECK SEAT POSITION MEMORY FUNCTION

(a) Check the seat position memory function.

Click here

OK:

Seat position memory function is normal.

NG

GO TO OTHER DIAGNOSIS PROCEDURE (Power Seat Position is not Memorized)

OK

3.	CHECK SEAT POSITION RESTORING FUNCTION

(a) Under each of the following conditions, check that the seat position restoring function operates by pressing the M1, M2 or M3 switch.

Click here

Result	Proceed to
Seat position restoring function does not operate at all.	A
Seat position restoring function does not operate when the condition is *1.	B
Seat position restoring function does not operate when the condition is *2. Seat position restoring function does not operate when the condition is *3.	C

B

GO TO STEP 9

C

GO TO STEP 10

A

4.	READ VALUE USING TECHSTREAM (SEAT POSITION MEMORY)

(a) Store a seat position in memory for the M1, M2 and M3 switches.

Click here

(b) Connect the Techstream to the DLC3.

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

(d) Turn the Techstream on.

(e) Enter the following menus: Body Electrical / Driver Seat / Data List.

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

Body Electrical > Driver Seat > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Seat Memory No1	Seat position memorized with M1 switch	Mem or Not Mem	Mem: Memorized Not Mem: Not memorized	-
Seat Memory No2	Seat position memorized with M2 switch	Mem or Not Mem	Mem: Memorized Not Mem: Not memorized	-
Seat Memory No3	Seat position memorized with M3 switch	Mem or Not Mem	Mem: Memorized Not Mem: Not memorized	-

Body Electrical > Driver Seat > Data List

Tester Display
Seat Memory No1
Seat Memory No2
Seat Memory No3

OK:

Mem is displayed on the Techstream screen.

NG

GO TO OTHER DIAGNOSIS PROCEDURE (Power Seat Position is not Memorized)

OK

5.	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

6.	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

7.	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

8.	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)

9.	READ VALUE USING TECHSTREAM (SHIFT P POSITION STATE)

(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 / Data List.

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

Body Electrical > Driver Seat > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
P Switch	Park state signal	ON or OFF	ON: Shift lever in P OFF: Shift lever in a position other than P	-

Body Electrical > Driver Seat > Data List

Tester Display
P Switch

OK:

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

OK

REPLACE POSITION CONTROL ECU AND SWITCH ASSEMBLY LH

NG

GO TO AUTOMATIC TRANSAXLE SYSTEM (P0705)

10.	READ VALUE USING TECHSTREAM (DRIVER DOOR COURTESY SWITCH)

(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 / Main Body / Data List.

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

Body Electrical > Main Body > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
FL Door Courtesy SW	Front door courtesy light switch assembly (driver door) signal*	ON or OFF	ON: Driver door open OFF: Driver door closed	-

Body Electrical > Main Body > Data List

Tester Display
FL Door Courtesy SW

OK:

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

OK

REPLACE POSITION CONTROL ECU AND SWITCH ASSEMBLY LH

NG

GO TO LIGHTING SYSTEM (Door Courtesy Switch Circuit)