Lexus NX: Seat Belt Buckle Switch (LH) (B1656)

DESCRIPTION

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

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

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1656

Seat Belt Buckle Switch (LH)

One of the following conditions is met:
  • The airbag ECU assembly detects a line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to B+ signal in the seat belt buckle switch LH circuit for 2 seconds.
  • A front seat inner belt assembly LH malfunction.
  • An airbag ECU assembly malfunction.
  • No. 2 floor wire
  • Front seat inner belt assembly LH
  • Airbag ECU assembly

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • After the power switch is turned off, there may be a waiting time before disconnecting the negative (-) auxiliary battery terminal.

    Click here

  • When disconnecting and reconnecting the auxiliary battery

    Click here

    HINT:

    When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

    Click here

  • After replacing the airbag ECU assembly, refer to initialization.

    Click here

PROCEDURE

1.

CHECK CONNECTION OF CONNECTORS

(a) Turn the power switch off.

(b) Disconnect the cable from the negative (-) auxiliary battery terminal, and wait for at least 90 seconds.

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

Connectors are not properly connected

CONNECT CONNECTORS PROPERLY

Connectors are properly connected

2.

CHECK CONNECTORS

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

*1

Front Seat Inner Belt Assembly LH

*2

Airbag ECU Assembly

*3

No. 2 Floor Wire

(b) Check that the connectors (on the airbag ECU assembly side and front seat inner belt assembly LH side) are not damaged.

Connectors are deformed or damaged

REPLACE NO. 2 FLOOR WIRE

Connectors are not deformed or damaged

3.

CHECK FLOOR WIRE NO.2

(a) Connect the cable to the negative (-) auxiliary battery terminal, and wait for at least 2 seconds.

*1

Front Seat Inner Belt Assembly LH

*2

Airbag ECU Assembly

*3

No. 2 Floor Wire

*4

Connector C

*5

Connector B

*6

Service Wire

*a

Front view of wire harness connector

(to Front Seat Inner Belt Assembly LH)

*b

Rear view of wire harness connector

(to Airbag ECU Assembly)

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

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

Q45-2 (LBE+) - Body ground

Power switch on (IG)

Below 1 V

Q45-1 (LBE-) - Body ground

Power switch on (IG)

Below 1 V

(d) Turn the power switch off.

(e) Disconnect the cable from the negative (-) auxiliary battery terminal, and wait for at least 90 seconds.

(f) Using a service wire, connect terminals 15 (LBE+) and 23 (LBE-) of connector B.

NOTICE:

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

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Q45-2 (LBE+) - Q45-1 (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

Q45-2 (LBE+) - Q45-1 (LBE-)

Always

1 MΩ or higher

Q45-2 (LBE+) - Body ground

Always

1 MΩ or higher

Q45-1 (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 ECU assembly and front seat inner belt assembly LH.

*1

Front Seat Inner Belt Assembly LH

*2

Airbag ECU Assembly

(b) Connect the cable to the negative (-) auxiliary battery terminal, and wait for at least 2 seconds.

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

(d) Clear the DTCs.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(e) Turn the power switch off.

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

(g) Check for DTCs.

Click here

Body Electrical > SRS Airbag > Trouble Codes

HINT:

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

DTC B1656 is not output

USE SIMULATION METHOD TO CHECK

DTC B1656 is output

5.

REPLACE FRONT SEAT INNER BELT ASSEMBLY LH

(a) Turn the power switch off.

(b) Disconnect the cable from the negative (-) auxiliary battery terminal, and wait for at least 90 seconds.

(c) Replace the front seat inner belt assembly LH.

Click here

HINT:

Perform the inspection using parts from a normal vehicle if possible.

NEXT

6.

CHECK DTC

(a) Connect the cable to the negative (-) auxiliary battery terminal, and wait for at least 2 seconds.

*1

Front Seat Inner Belt Assembly LH

*2

Airbag ECU Assembly

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

(c) Clear the DTCs.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(d) Turn the power switch off.

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

(f) Check for DTCs.

Click here

Body Electrical > SRS Airbag > Trouble Codes

HINT:

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

DTC B1656 is not output

END (FRONT SEAT INNER BELT ASSEMBLY LH WAS DEFECTIVE)

DTC B1656 is output

REPLACE AIRBAG ECU ASSEMBLY

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