Toyota 4Runner: Seat Belt Buckle Switch LH Circuit Malfunction (B1656/38)

Toyota 4Runner Service Manual / Vehicle Interior / Supplemental Restraint Systems / Airbag System / Seat Belt Buckle Switch LH Circuit Malfunction (B1656/38)

DESCRIPTION

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

DTC B1656/37 is stored when a malfunction is detected in the seat belt buckle switch LH circuit.

DTC Code	DTC Detection Condition	Trouble Area
B1656/38	One of the following conditions is met: The center airbag sensor 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 LH malfunction. A center airbag sensor malfunction.	No. 2 floor wire Front seat inner belt assembly LH (Seat belt buckle switch LH) Center airbag sensor assembly

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When disconnecting the cable from the negative (-) battery terminal while performing repairs, some systems need to be initialized after the cable is reconnected (See page ).

PROCEDURE

1.	CHECK FOR DTC

(a) Turn the ignition switch to ON.

(b) Clear the DTCs (See page ).

(d) Turn the ignition switch to ON, and wait for at least 60 seconds.

(e) Check for DTCs (See page ).

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.

USE SIMULATION METHOD TO CHECK

2.	CHECK CONNECTION OF CONNECTORS

(a) Turn the ignition switch off.

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

OK:

The connectors are properly connected.

CONNECT CONNECTORS PROPERLY

3.	CHECK CONNECTORS

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

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

OK:

The connectors are not deformed or damaged.

Text in Illustration

*1	Front Seat Inner Belt LH
*2	Center Airbag Sensor

REPLACE NO. 2 FLOOR WIRE

4.	CHECK NO. 2 FLOOR WIRE (CENTER AIRBAG SENSOR - FRONT SEAT INNER BELT LH)

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

Text in Illustration

*1	Front Seat Inner Belt LH	*2	Center Airbag Sensor
*3	No. 2 Floor Wire	*4	Connector C
*5	Connector B	-	-
*a	Front view of wire harness connector (to Front Seat Inner Belt LH)	*b	Rear view of wire harness connector (to Center Airbag Sensor)

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
O3-2 (LBE+) - Body ground	Ignition switch ON	Below 1 V
O3-1 (LBE-) - Body ground	Ignition switch ON	Below 1 V

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
O3-2 (LBE+) - O1-10 (LBE+)	Always	Below 1 Ω
O3-2 (LBE+) - Body ground	Always	1 MΩ or higher
O3-1 (LBE-) - O1-18 (LBE-)	Always	Below 1 Ω
O3-1 (LBE-) - Body ground	Always	1 MΩ or higher

REPLACE NO. 2 FLOOR WIRE

5.	CHECK FRONT SEAT INNER BELT LH (SEAT BELT BUCKLE SWITCH)

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

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

(d) Clear the DTCs (See page ).

(e) Turn the ignition switch off.

(f) Turn the ignition switch to ON, and wait for at least 60 seconds.

(g) Check for DTCs (See page ).

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.

Text in Illustration

*1	Front Seat Inner Belt LH
*2	Center Airbag Sensor

USE SIMULATION METHOD TO CHECK

6.	REPLACE FRONT SEAT INNER BELT ASSEMBLY LH

(a) Turn the ignition switch off.

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

HINT:

Perform the inspection using parts from a normally functioning vehicle if possible.

7.	CHECK CENTER AIRBAG SENSOR

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

(b) Turn the ignition switch to ON, and wait for at least 60 seconds.

(d) Turn the ignition switch off.

(e) Turn the ignition switch to ON, and wait for at least 60 seconds.

(f) Check for DTCs (See page ).

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.

Text in Illustration

*1	Front Seat Inner Belt LH
*2	Center Airbag Sensor

REPLACE FRONT SEAT INNER BELT ASSEMBLY LH

REPLACE CENTER AIRBAG SENSOR ASSEMBLY

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