DTC B1771: Passenger Side Buckle Switch Circuit Malfunction [12/2017 - 10/2020]: Procedure

1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal.
3. 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.

4. Disconnect the connectors from the occupant detection ECU and front seat inner belt assembly RH.
5. Check that the terminals of the connectors are not deformed or damaged.

   OK

   The terminals are not deformed or damaged.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE FRONT SEAT WIRE RH 

Result: 

OK 

See step  2

1. 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
   *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)

2. Turn the engine switch on (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   Q41-7 (BSW) - Body ground	Engine switch on (IG)	Below 1 V
   Q41-9 (BGND) - Body ground

4. Turn the engine switch off.
5. Disconnect the cable from the negative (-) battery terminal.
6. 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.

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Q41-7 (BSW) - Q41-9 (BGND)	Always	Below 1 Ω

8. Disconnect the service wire from connector C.
9. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Q41-7 (BSW) - Q41-9 (BGND)	Always	1 MΩ or higher
   Q41-7 (BSW) - Body ground
   Q41-9 (BGND) - Body ground

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE FRONT SEAT WIRE RH 

Result: 

OK 

See step  3

1. Connect the connectors to the occupant detection ECU and front seat inner belt assembly RH.
2. Connect the cable to the negative (-) battery terminal.
3. Clear the DTCs stored in the occupant detection ECU.

   Refer to DTC CHECK / CLEAR [12/2017 - 10/2023]

   Body Electrical > Occupant Detection > Clear DTCs 

4. Clear the DTCs stored in the airbag ECU assembly.

   Refer to DTC CHECK / CLEAR [12/2017 - 10/2023]

   Body Electrical > SRS Airbag > Clear DTCs 

5. Turn the engine switch off.
6. Turn the engine switch on (IG), and wait for at least 10 seconds.
7. Check for DTCs.

   Refer to DTC CHECK / CLEAR [12/2017 - 10/2023]

   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.

8. Turn the engine switch off.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2017 - 09/2018]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [09/2018 - 10/2020] 

Result: 

NG 

See step  4

1. Disconnect the cable from the negative (-) battery terminal.
2. Replace the front seat inner belt assembly RH with a new one.

   Refer to REMOVAL [12/2017 - 09/2018] , or refer to REMOVAL [09/2018 - 10/2020]

   HINT: 

   Perform the following inspection using known good parts from another vehicle if possible.

3. Connect the cable to the negative (-) battery terminal.
4. Clear the DTCs stored in the occupant detection ECU.

   Refer to DTC CHECK / CLEAR [12/2017 - 10/2023]

   Body Electrical > Occupant Detection > Clear DTCs 

5. Clear the DTCs stored in the airbag ECU assembly.

   Refer to DTC CHECK / CLEAR [12/2017 - 10/2023]

   Body Electrical > SRS Airbag > Clear DTCs 

6. Turn the engine switch off.
7. Turn the engine switch on (IG), and wait for at least 10 seconds.
8. Check for DTCs.

   Refer to DTC CHECK / CLEAR [12/2017 - 10/2023]

   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.

9. Turn the engine switch off.
10. Disconnect the cable from the negative (-) battery terminal.
11. Restore the front seat inner belt assembly RH that was installed for testing to its original location.

    Refer to REMOVAL [12/2017 - 09/2018] , or refer to REMOVAL [09/2018 - 10/2020]

    Result

    Proceed to
    OK
    NG

Result: 

OK 

END (FRONT SEAT INNER BELT ASSEMBLY RH WAS DEFECTIVE) 

Result: 

NG 

See step  5

1. Turn the engine switch off.
2. Disconnect the cable from the negative (-) battery terminal.
3. Replace the occupant detection ECU with a new one.

   Refer to REMOVAL [12/2017 - 09/2018] , or refer to REMOVAL [09/2018 - 10/2020]

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

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  6

1. Using the Techstream, perform Zero Point Calibration.

   Refer to INITIALIZATION [12/2017 - 10/2023]

   Body Electrical > Occupant Detection > Utility 

   Tester Display
   Zero Point Calibration

   Result

   Proceed to
   NEXT

Result: 

NEXT 

END (OCCUPANT DETECTION ECU WAS DEFECTIVE)