Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Front Passenger Side Seat Belt Warning Light Malfunction

DESCRIPTION

When the engine switch is turned on (IG), the occupant detection ECU sends signals to the airbag sensor assembly to indicate the state of the front seat inner belt assembly RH and also whether the front passenger seat is occupied. The airbag sensor assembly sends those signals to the combination meter assembly via CAN communication. The seat belt warning light on the combination meter assembly illuminates, blinks or turns off in accordance with these signals.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

The seat belt warning system uses the CAN communication system. First, confirm that there are no malfunctions in the CAN communication system. Refer to How to Proceed with Troubleshooting.

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PROCEDURE

1.	CHECK DTC OUTPUT (OCCUPANT CLASSIFICATION SYSTEM)

(a) Clear the DTCs.

Click here

Body Electrical > Occupant Detection > Clear DTCs

(b) Check for DTCs.

Click here

Body Electrical > Occupant Detection > Trouble Codes

Result	Proceed to
DTCs are not output	A
DTCs are output	B

B

GO TO OCCUPANT CLASSIFICATION SYSTEM

A

2.	CHECK DTC OUTPUT (AIRBAG SYSTEM)

(a) Clear the DTCs.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(b) Check for DTCs.

Click here

Body Electrical > SRS Airbag > Trouble Codes

Result	Proceed to
DTCs are not output	A
DTCs are output	B

B

GO TO AIRBAG SYSTEM

A

3.	READ VALUE USING TECHSTREAM

(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 / Occupant Detection / Data List.

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

Body Electrical > Occupant Detection > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Passenger Buckle SW	Front passenger buckle switch	Unset, Set or NG	Unset: Seat belt not fastened Set: Seat belt fastened NG: Data is not determined	-

Body Electrical > Occupant Detection > Data List

Tester Display
The Number of DTCs

Result	Proceed to
Unset or Set is displayed on the Techstream according to the front passenger seat belt condition	A
Unset or Set is not displayed correctly on the Techstream according to the front passenger seat belt condition	B
NG is displayed on the Techstream	C

B

REPLACE FRONT SEAT INNER BELT ASSEMBLY RH

C

REPLACE OCCUPANT DETECTION ECU

A

4.	READ VALUE USING TECHSTREAM

(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 / SRS Airbag / Data List.

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

Body Electrical > SRS Airbag > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Right side Buckle SW	RH buckle switch	Unset, Set or NG	Unset: Seat belt not fastened Set: Seat belt fastened NG: Data is not determined	-

Body Electrical > SRS Airbag > Data List

Tester Display
Right side Buckle SW

Result	Proceed to
Unset or Set is displayed on the Techstream according to the front passenger seat belt condition	A
Unset or Set is not displayed correctly on the Techstream according to the front passenger seat belt condition NG is displayed on the Techstream	B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE AIRBAG SENSOR ASSEMBLY