DTC B1771: Passenger Side Buckle Switch Circuit Malfunction [12/2019 - 10/2021]: Procedure

CHECK CONNECTORS

Turn the ignition switch off.
Disconnect the cable from the negative (-) auxiliary 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

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

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)

Turn the ignition switch to ON.

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

Standard Voltage

Tester Connection	Condition	Specified Condition
e2-7 (BSW) - Body ground	Ignition switch ON	Below 1 V
e2-9 (BGND) - Body ground	Ignition switch ON	Below 1 V

Turn the ignition switch off.
Disconnect the cable from the negative (-) auxiliary battery terminal.
Using a service wire, connect terminals 1 (+) and 2 (-) of connector C.
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
e2-7 (BSW) - e2-9 (BGND)	Always	Below 1 Ω

Disconnect the service wire from connector C.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
e2-7 (BSW) - e2-9 (BGND)	Always	1 MΩ or higher
e2-7 (BSW) - Body ground	Always	1 MΩ or higher
e2-9 (BGND) - Body ground	Always	1 MΩ or higher

Result

Proceed to
OK
NG

Result:

REPLACE FRONT SEAT WIRE RH

Result:

See step 3

CHECK DTC

Connect the connectors to the occupant detection ECU and front seat inner belt assembly RH.
Connect the cable to the negative (-) auxiliary battery terminal.
Turn the ignition switch to ON, and wait for at least 60 seconds.
Clear the DTCs stored in the occupant detection ECU.
Body Electrical > Occupant Detection > Clear DTCs
Clear the DTCs stored in the airbag sensor assembly.
Body Electrical > SRS Airbag > Clear DTCs
Turn the ignition switch off.
Turn the ignition switch to ON, and wait for at least 10 seconds.
Check for DTCs.
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 ignition switch off.

Result

Proceed to
OK
NG

Result:

USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [12/2019 - ]

Result:

See step 4

CHECK FRONT SEAT INNER BELT ASSEMBLY RH

Disconnect the cable from the negative (-) auxiliary battery terminal.
Replace the front seat inner belt assembly RH with a known good one.
for Manual Seat: Refer to REMOVAL [12/2019 - 10/2022]

for Power Seat: Refer to REMOVAL [12/2019 - 10/2022]

HINT:

Perform the following inspection using known good parts from another vehicle if possible.
Connect the cable to the negative (-) auxiliary battery terminal.
Turn the ignition switch to ON, and wait for at least 60 seconds.
Clear the DTCs stored in the occupant detection ECU.
Body Electrical > Occupant Detection > Clear DTCs
Clear the DTCs stored in the airbag sensor assembly.
Body Electrical > SRS Airbag > Clear DTCs
Turn the ignition switch off.
Turn the ignition switch to ON, and wait for at least 10 seconds.
Check for DTCs.
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 ignition switch off.
Disconnect the cable from the negative (-) auxiliary battery terminal.

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

for Manual Seat: Refer to REMOVAL [12/2019 - 10/2022]

for Power Seat: Refer to REMOVAL [12/2019 - 10/2022]

Result

Proceed to
OK
NG

Result:

REPLACE FRONT SEAT INNER BELT ASSEMBLY RH

for Manual Seat: Refer to REMOVAL [12/2019 - 10/2022]

for Power Seat: Refer to REMOVAL [12/2019 - 10/2022]

Result:

See step 5

REPLACE OCCUPANT DETECTION ECU

Turn the ignition switch off.
Disconnect the cable from the negative (-) auxiliary battery terminal.
Replace the occupant detection ECU with a new one.
Refer to REMOVAL [12/2019 - 10/2022]

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

Result

Proceed to
NEXT

Result:

See step 6

PERFORM ZERO POINT CALIBRATION

Using the GTS, perform Zero Point Calibration.

Refer to INITIALIZATION [12/2019 - 10/2021]

Result

Proceed to
NEXT

Result:

END