DTC B1771: Passenger Side Buckle Switch Circuit Malfunction [09/2014 - 03/2019]: Procedure

CHECK CONNECTORS

Turn the engine switch off.
Disconnect the cable from the negative (-) battery terminal.
Check that the connectors are properly connected to the occupant detection ECU and front seat inner belt assembly RH.
OK

The connectors are properly connected.

HINT:

If the connectors are not properly connected, reconnect the connectors and proceed to the next inspection.
Disconnect the connectors from the occupant detection ECU and front seat inner belt assembly RH.

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

The terminals are not deformed or damaged.

Result

Proceed to
OK
NG

Result:

REPLACE FRONT SEAT WIRE RH

Result:

See step 2

CHECK FRONT SEAT WIRE RH (SHORT TO B+)

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

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*1	Front Seat Inner Belt Assembly RH
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*a	Front view of wire harness connector (to Occupant Detection ECU)

Turn the engine switch on (IG).

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

Standard Voltage

Tester Connection	Condition	Specified Condition
a15-8 (BSW) - Body ground	Engine switch on (IG)	Below 1 V
a15-5 (BGND) - Body ground	Engine switch on (IG)	Below 1 V

Turn the engine switch off.

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

Result

Proceed to
OK
NG

Result:

REPLACE FRONT SEAT WIRE RH

Result:

See step 3

CHECK FRONT SEAT WIRE RH (OPEN)

Using a service wire, connect terminals 1 (+) and 2 (-) of connector C.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*1	Front Seat Inner Belt Assembly RH
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*4	Service Wire
*a	Front view of wire harness connector (to Occupant Detection ECU)
*b	Front view of wire harness connector (to Front Seat Inner Belt Assembly RH)

NOTE:

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

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

Standard Resistance

Tester Connection	Condition	Specified Condition
a15-8 (BSW) - a15-5 (BGND)	Always	Below 1 Ω

Disconnect the service wire from connector C.

Result

Proceed to
OK
NG

Result:

REPLACE FRONT SEAT WIRE RH

Result:

See step 4

CHECK FRONT SEAT WIRE RH (SHORT)

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

Standard Resistance

Tester Connection	Condition	Specified Condition
a15-8 (BSW) - a15-5 (BGND)	Always	1 MΩ or higher

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*1	Front Seat Inner Belt Assembly RH
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*a	Front view of wire harness connector (to Occupant Detection ECU)

Result

Proceed to
OK
NG

Result:

REPLACE FRONT SEAT WIRE RH

Result:

See step 5

CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

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

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*1	Front Seat Inner Belt Assembly RH
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*a	Front view of wire harness connector (to Occupant Detection ECU)

Standard Resistance

Tester Connection	Condition	Specified Condition
a15-8 (BSW) - Body ground	Always	1 MΩ or higher
a15-5 (BGND) - Body ground	Always	1 MΩ or higher

Result

Proceed to
OK
NG

Result:

REPLACE FRONT SEAT WIRE RH

Result:

See step 6

CHECK DTC

Connect the connectors to the occupant detection ECU and front seat inner belt assembly RH.
Connect the cable to the negative (-) battery terminal.
Clear the DTCs stored in the occupant detection ECU.
Refer to DTC CHECK / CLEAR [09/2014 - ]

Body Electrical > Occupant Detection > Clear DTCs
Clear the DTCs stored in the airbag ECU assembly.
Refer to DTC CHECK / CLEAR [09/2014 - 03/2019]

Body Electrical > SRS Airbag > Clear DTCs
Turn the engine switch off.
Turn the engine switch on (IG), and wait for at least 10 seconds.
Check for DTCs.
Refer to DTC CHECK / CLEAR [09/2014 - ]

Body Electrical > Occupant Detection > Trouble Codes

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.

Turn the engine switch off.

Result

Proceed to
OK
NG

Result:

USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [09/2014 - 08/2016] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2016 - 11/2017] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [11/2017 - 03/2019]

Result:

See step 7

CHECK FRONT SEAT INNER BELT ASSEMBLY RH

Disconnect the cable from the negative (-) battery terminal.
Replace the front seat inner belt assembly RH with a known good one.
Refer to REMOVAL [09/2014 - ]

HINT:

Perform the following inspection using known good parts from another vehicle if possible.
Connect the cable to the negative (-) battery terminal.
Clear the DTCs stored in the occupant detection ECU.
Refer to DTC CHECK / CLEAR [09/2014 - ]

Body Electrical > Occupant Detection > Clear DTCs
Clear the DTCs stored in the airbag ECU assembly.
Refer to DTC CHECK / CLEAR [09/2014 - 03/2019]

Body Electrical > SRS Airbag > Clear DTCs
Turn the engine switch off.
Turn the engine switch on (IG), and wait for at least 10 seconds.
Check for DTCs.
Refer to DTC CHECK / CLEAR [09/2014 - ]

Body Electrical > Occupant Detection > Trouble Codes

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.
Turn the engine switch off.
Disconnect the cable from the negative (-) battery terminal.

Restore the front seat inner belt assembly RH that was installed for testing to its original location.

Refer to REMOVAL [09/2014 - ]

Result

Proceed to
OK
NG

Result:

REPLACE FRONT SEAT INNER BELT ASSEMBLY RH. Refer to REMOVAL [09/2014 - ]

Result:

See step 8

REPLACE OCCUPANT DETECTION ECU

Turn the engine switch off.
Disconnect the cable from the negative (-) battery terminal.
Replace the occupant detection ECU with a new one.
Refer to REMOVAL [09/2014 - ]

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

Result

Proceed to
NEXT

Result:

See step 9

PERFORM ZERO POINT CALIBRATION AND SENSITIVITY CHECK

Using the Techstream, perform zero point calibration and sensitivity check.

Refer to INITIALIZATION [09/2014 - ]

Body Electrical > Occupant Detection > Utility

Tester Display
Zero Point Calibration & Sensitivity Check

Result

Proceed to
NEXT

Result:

END