Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Driver Side Seat Position Sensor (B1653)

DESCRIPTION

The seat position airbag sensor circuit consists of the airbag sensor assembly and seat position airbag sensor.

DTC B1653 is stored when a malfunction is detected in the seat position airbag sensor circuit.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Warning Indicate	Test Mode / Check Mode
B1653	Driver Side Seat Position Sensor	The airbag sensor assembly detects a line short, short to ground or B+, or an open in the seat position airbag sensor circuit. Seat position airbag sensor malfunction Airbag sensor assembly malfunction	No. 2 floor wire Front seat inner belt assembly LH Seat position airbag sensor Airbag sensor assembly	Comes on	Does not apply to test/check mode

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

Click here

PROCEDURE

1.	CHECK CONNECTION OF CONNECTORS

(a) Turn the engine switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(c) Check that the connectors are properly connected to the airbag sensor assembly, front seat inner belt assembly LH and seat position airbag sensor.

OK:

The connectors are properly connected.

NG

CONNECT CONNECTORS PROPERLY

OK

2.	CHECK CONNECTORS

(a) Disconnect the connectors from the airbag sensor assembly, front seat inner belt assembly LH and seat position airbag sensor.

(b) Check that the terminals of the connectors are not deformed or damaged.

OK:

The terminals are not deformed or damaged.

NG

REPLACE NO. 2 FLOOR WIRE OR FRONT SEAT INNER BELT ASSEMBLY LH

OK

3.	CHECK WIRE HARNESS

(a) Connect the connectors to the front seat inner belt assembly LH and No. 2 floor wire.

*1 Seat Position Airbag Sensor *2 Front Seat Inner Belt Assembly LH *3 Airbag Sensor Assembly *4 No. 2 Floor Wire *5 Service Wire *a Front view of wire harness connector (to Airbag Sensor Assembly) *b Front view of wire harness connector (to Seat Position Airbag Sensor)

(b) Connect the cable to the negative (-) battery terminal.

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

(d) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection	Condition	Specified Condition
2 (LSP+) - Body ground	Engine switch on (IG)	Below 1 V
1 (LSP-) - Body ground	Engine switch on (IG)	Below 1 V

(e) Turn the engine switch off.

(f) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(g) Using a service wire, connect terminals 25 (LSP+) and 26 (LSP-) of connector B.

NOTICE:

Do not forcibly insert the service wire into the terminals of the connector when connecting the wire.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
2 (LSP+) - 1 (LSP-)	Always	Below 1 Ω

(i) Disconnect the service wire from connector B.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
2 (LSP+) - 1 (LSP-)	Always	1 MΩ or higher
2 (LSP+) - Body ground	Always	1 MΩ or higher
1 (LSP-) - Body ground	Always	1 MΩ or higher

NG

GO TO STEP 6

OK

4.

CHECK DTC

(a) Connect the connectors to the airbag sensor assembly and seat position airbag sensor.

*1 Seat Position Airbag Sensor *2 Front Seat Inner Belt Assembly LH *3 Airbag Sensor Assembly

(b) Connect the cable to the negative (-) battery terminal.

(c) Turn the engine switch on (IG), and wait for at least 60 seconds.

(d) Clear the DTCs stored in memory.

Body Electrical > SRS Airbag > Clear DTCs

(e) Turn the engine switch off.

(f) Turn the engine switch on (IG), and wait for at least 60 seconds.

(g) Check for DTCs.

Body Electrical > SRS Airbag > Trouble Codes

OK:

DTC B1653 is not output.

HINT:

Codes other than DTC B1653 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK

NG

5.	CHECK SEAT POSITION AIRBAG SENSOR

(a) Turn the engine switch off.

*1 Seat Position Airbag Sensor *2 Front Seat Inner Belt Assembly LH *3 Airbag Sensor Assembly

(b) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(c) Replace the seat position airbag sensor with a known good one.

Click here

HINT:

Perform the following inspection using known good parts from another vehicle if possible.

(d) Connect the cable to the negative (-) battery terminal.

(e) Turn the engine switch on (IG), and wait for at least 60 seconds.

(f) Clear the DTCs stored in memory.

Body Electrical > SRS Airbag > Clear DTCs

(g) Turn the engine switch off.

(h) Turn the engine switch on (IG), and wait for at least 60 seconds.

(i) Check for DTCs.

Body Electrical > SRS Airbag > Trouble Codes

OK:

DTC B1653 is not output.

HINT:

Codes other than DTC B1653 may be output at this time, but they are not related to this check.

(j) Turn the engine switch off.

(k) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(l) Restore the seat position airbag sensor that was installed for testing to its original location.

Click here

OK

REPLACE SEAT POSITION AIRBAG SENSOR

NG

REPLACE AIRBAG SENSOR ASSEMBLY

6.	CHECK NO. 2 FLOOR WIRE

(a) Disconnect the No. 2 floor wire connector from the front seat inner belt assembly LH.

*1 Seat Position Airbag Sensor *2 Front Seat Inner Belt Assembly LH *3 Airbag Sensor Assembly *4 No. 2 Floor Wire *5 Service Wire *a Front view of wire harness connector (to Airbag Sensor Assembly) *b Front view of wire harness connector (to Front Seat Inner Belt Assembly LH)

(b) Connect the cable to the negative (-) battery terminal.

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

(d) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection	Condition	Specified Condition
S6-4 (LSP+) - Body ground	Engine switch on (IG)	Below 1 V
S6-3 (LSP-) - Body ground	Engine switch on (IG)	Below 1 V

(e) Turn the engine switch off.

(f) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(g) Using a service wire, connect terminals 25 (LSP+) and 26 (LSP-) of connector B.

NOTICE:

Do not forcibly insert the service wire into the terminals of the connector when connecting the wire.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S6-4 (LSP+) - S6-3 (LSP-)	Always	Below 1 Ω

(i) Disconnect the service wire from connector B.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S6-4 (LSP+) - S6-3 (LSP-)	Always	1 MΩ or higher
S6-4 (LSP+) - Body ground	Always	1 MΩ or higher
S6-3 (LSP-) - Body ground	Always	1 MΩ or higher

OK

REPLACE FRONT SEAT INNER BELT ASSEMBLY LH

NG

REPLACE NO. 2 FLOOR WIRE