Toyota Tacoma 2015-2018 Service Manual: Passenger Side Buckle Switch Circuit Malfunction (B1771)

Toyota Tacoma 2015-2018 Service Manual / Supplemental Restraint Systems / Occupant Classification System / Passenger Side Buckle Switch Circuit Malfunction (B1771)

DESCRIPTION

The passenger side buckle switch circuit consists of the occupant detection ECU and the front seat inner belt assembly RH.

DTC B1771 is recorded when a malfunction is detected in the passenger side buckle switch circuit.

Troubleshoot DTC B1771 first when DTCs B1771 and B1795 are output simultaneously.

DTC No.	DTC Detecting Condition	Trouble Area
B1771	Occupant detection ECU detects line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to B+ signal in the passenger side buckle switch circuit for 2 seconds Passenger side buckle switch malfunction Occupant detection ECU malfunction	No .1 seat wire Floor wire Front seat inner belt assembly RH (Buckle switch RH) Occupant detection ECU

HINT:

When DTC B1650/32 is detected as a result of troubleshooting the supplemental restraint system, perform troubleshooting for DTC B1771 of the occupant classification system.
Use the Techstream to check for DTCs of the occupant detection ECU, otherwise the DTC cannot be read.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see the under surface of the seat cushion.
In the above case, hold the seat so that it does not tip over. Holding the seat for a long period of time may cause a problem, such as seat rail deformation. Hold the seat up only for as long as necessary.

PROCEDURE

CHECK DTC

(a) Turn the ignition switch to the on position.

(b) Clear the DTCs stored in the memory (See page HINT: ).

HINT:

First clear DTCs stored in the occupant detection ECU and then in the airbag sensor assembly.

(d) Turn the ignition switch to the on position.

(e) Check the DTCs (See page OK: ).

OK:

DTC B1771 is not output.

HINT:

Codes other than DTC B1771 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 to the lock position.

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

(c) Check that the connectors are properly connected to the occupant detection ECU and the front seat inner belt assembly RH.

OK:

The connectors are properly connected.

CONNECT CONNECTORS

3.	CHECK CONNECTORS

(a) Check that the connectors (on the occupant detection ECU side and buckle switch RH side) are not damaged (See page OK: ).

OK:

The connectors are not deformed or damaged.

REPAIR OR REPLACE WIRE HARNESS

4.	CHECK NO. 1 SEAT WIRE (TO B+)

(a) Disconnect the connectors from the occupant detection ECU and the front seat inner belt assembly RH.

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

(d) Measure the voltage.

Standard voltage:

Tester connection	Condition	Specified condition
O5-9 (BSW) - Body ground	Ignition switch on	Below 1 V
O5-5 (BGND) - Body ground	Ignition switch on	Below 1 V

Tester connection

Condition

Specified condition

O5-9 (BSW) -

Body ground

Ignition switch on

Below 1 V

O5-5 (BGND) -

Body ground

Ignition switch on

Below 1 V

REPAIR OR REPLACE NO. 1 SEAT WIRE

5.	CHECK NO. 1 SEAT WIRE (FOR OPEN)

(a) Turn the ignition switch to the lock position.

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

NOTICE:

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

(d) Measure the resistance.

Standard resistance:

Tester connection	Condition	Specified condition
O5-9 (BSW) - O5-5 (BGND)	Always	Below 1 Ω

Tester connection

Condition

Specified condition

O5-9 (BSW) -

O5-5 (BGND)

Always

Below 1 Ω

REPAIR OR REPLACE NO. 1 SEAT WIRE

6.	CHECK NO. 1 SEAT WIRE (FOR SHORT)

(a) Disconnect the service wire from connector C.

(b) Measure the resistance.

Standard resistance:

Tester connection	Condition	Specified condition
O5-9 (BSW) - O5-5 (BGND)	Always	1 MΩ or higher

Tester connection

Condition

Specified condition

O5-9 (BSW) -

O5-5 (BGND)

Always

1 MΩ or higher

REPAIR OR REPLACE NO. 1 SEAT WIRE

7.	CHECK NO. 1 SEAT WIRE (TO GROUND)

(a) Measure the resistance.

Standard resistance:

Tester connection

Condition

Specified condition

O5-9 (BSW) -

Body ground

Always

1 MΩ or higher

O5-5 (BGND) -

Body ground

Always

1 MΩ or higher

REPAIR OR REPLACE NO. 1 SEAT WIRE

CHECK DTC

(a) Connect the connectors to the occupant detection ECU and the front seat inner belt assembly RH.

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

(d) Clear the DTCs stored in the memory (See page HINT: ).

HINT:

First clear DTCs stored in the occupant detection ECU and then in the airbag sensor assembly.

(e) Turn the ignition switch to the lock position.

(f) Turn the ignition switch to the on position.

(g) Check the DTCs (See page OK: ).

OK:

DTC B1771 is not output.

HINT:

Codes other than DTC B1771 may be output at this time, but they are not related to this check.

USE SIMULATION METHOD TO CHECK

9.	REPLACE FRONT SEAT INNER BELT ASSEMBLY RH

(a) Turn the ignition switch to the lock position.

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

HINT:

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

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

(e) Turn the ignition switch to the on position.

(f) Clear the DTCs stored in the memory (See page HINT: ).

HINT:

First clear DTCs stored in the occupant detection ECU and then in the airbag sensor assembly.

(g) Turn the ignition switch to the lock position.

(h) Turn the ignition switch to the on position.

(i) Check the DTCs (See page OK: ).

OK:

DTC B1771 is not output.

HINT:

Codes other than DTC B1771 may be output at this time, but they are not related to this check.

END

10.	REPLACE OCCUPANT DETECTION ECU

(a) Turn the ignition switch to the lock position.

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

11.	PERFORM ZERO POINT CALIBRATION

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

(b) Connect the Techstream to the DLC3.

(d) Using the Techstream, perform the zero point calibration (See page OK: ).

OK:

"Zero Point Calibration is complete." is displayed on the Techstream.

12.	PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform the sensitivity check (See page Standard values: ).

Standard values:

27 to 33 kg (59.52 to 72.75 lb)

END

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