Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Seat Belt Buckle Switch (LH) (B1656)

DESCRIPTION

The front seat belt buckle switch LH circuit consists of the airbag sensor assembly and front seat belt buckle switch LH (front seat inner belt assembly LH).

DTC B1656 is stored when a malfunction is detected in the front seat belt buckle switch LH circuit.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Warning Indicate	Test Mode / Check Mode
B1656	Seat Belt Buckle Switch (LH)	The airbag sensor assembly detects a line short, short to ground or B+, or an open in the front seat belt buckle switch LH circuit. Front seat belt buckle switch LH malfunction Airbag sensor assembly malfunction	No. 2 floor wire Front seat belt buckle switch LH (Front seat inner belt assembly LH) 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.

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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 and front seat inner belt assembly LH.

OK:

The connectors are properly connected.

NG

CONNECT CONNECTORS PROPERLY

OK

2.	CHECK CONNECTORS

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

(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 NO. 2 FLOOR WIRE

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

*1 Front Seat Inner Belt Assembly LH *2 Airbag Sensor Assembly *3 No. 2 Floor Wire *4 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) Turn the engine switch on (IG).

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
S6-2 (LBE+) - Body ground	Engine switch on (IG)	Below 1 V
S6-1 (LBE-) - Body ground	Engine switch on (IG)	Below 1 V

(d) Turn the engine switch off.

(e) 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.

(f) Using a service wire, connect terminals 28 (LBE+) and 27 (LBE-) of connector B.

NOTICE:

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S6-2 (LBE+) - S6-1 (LBE-)	Always	Below 1 Ω

(h) Disconnect the service wire from connector B.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S6-2 (LBE+) - S6-1 (LBE-)	Always	1 MΩ or higher
S6-2 (LBE+) - Body ground	Always	1 MΩ or higher
S6-1 (LBE-) - Body ground	Always	1 MΩ or higher

NG

REPLACE NO. 2 FLOOR WIRE

OK

4.

CHECK DTC

(a) Connect the connectors to the airbag sensor assembly and front seat inner belt assembly LH.

*1 Front Seat Inner Belt Assembly LH *2 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 B1656 is not output.

HINT:

Codes other than DTC B1656 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK

NG

5.	CHECK FRONT SEAT INNER BELT ASSEMBLY LH

(a) Turn the engine switch off.

*1 Front Seat Inner Belt Assembly LH *2 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 front seat inner belt assembly LH with a known good one.

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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 B1656 is not output.

HINT:

Codes other than DTC B1656 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 front seat inner belt assembly LH that was installed for testing to its original location.

Click here

OK

REPLACE FRONT SEAT INNER BELT ASSEMBLY LH

NG

REPLACE AIRBAG SENSOR ASSEMBLY