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DTC B1771: Passenger Side Buckle Switch Circuit Malfunction [11/2018 - 02/2019]: Procedure

  1. CHECK CONNECTION OF CONNECTORS 
    1. Turn the ignition switch off.
    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    3. Check that the connectors are properly connected to the occupant detection ECU and front seat inner belt assembly RH.

      Result

      Proceed to
      Connectors are properly connected
      Connectors are not properly connected

    Result: 

    Connectors are not properly connected 

    CONNECT CONNECTORS PROPERLY 

    Result: 

    Connectors are properly connected 

    See step  2

  2. CHECK CONNECTORS 
    1. Disconnect the connectors from the occupant detection ECU and front seat inner belt assembly RH.
    2. Check that the connectors (on the occupant detection ECU side and front seat inner belt assembly RH side) are not damaged.

      Result

      Proceed to
      Connectors are not deformed or damaged
      Connectors are deformed or damaged

    Result: 

    Connectors are deformed or damaged 

    REPLACE FRONT SEAT WIRE RH. Refer to  DISASSEMBLY [11/2018 - 08/2020] 

    Result: 

    Connectors are not deformed or damaged 

    See step  3

  3. CHECK FRONT SEAT WIRE RH 
    1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
      GTY908582Courtesy 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 ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      S21-7 - Body ground Ignition switch ON Below 1 V
      S21-9 - Body ground
    4. Turn the ignition switch off.
    5. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    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 a service wire.

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      S21-7 - S21-9 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
      S21-7 - S21-9 Always 1 MΩ or higher
      S21-7 - Body ground
      S21-9 - Body ground

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE FRONT SEAT WIRE RH. Refer to  DISASSEMBLY [11/2018 - 08/2020] 

    Result: 

    OK 

    See step  4

  4. CHECK DTC 
    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, and wait for at least 2 seconds.
    3. Turn the ignition switch to ON, and wait for at least 60 seconds.
    4. Clear the DTCs stored in the occupant detection ECU.

      Refer to DTC CHECK / CLEAR [11/2018 - ]

      Body Electrical > Occupant Detection > Clear DTCs 

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

      Refer to DTC CHECK / CLEAR [11/2018 - ]

      Body Electrical > SRS Airbag > Clear DTCs 

    6. Turn the ignition switch off.
    7. Turn the ignition switch to ON, and wait for at least 60 seconds.
    8. Check the DTCs stored in the occupant detection ECU.

      Refer to DTC CHECK / CLEAR [11/2018 - ]

      Body Electrical > Occupant Detection > Trouble Codes 

      Result

      Proceed to
      DTC B1771 is output
      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.

    Result: 

    DTC B1771 is not output 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2018 - ] 

    Result: 

    DTC B1771 is output 

    See step  5

  5. REPLACE FRONT SEAT INNER BELT ASSEMBLY RH 
    1. Turn the ignition switch off.
    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    3. Replace the front seat inner belt assembly RH with a new one.

      Refer to REMOVAL [11/2018 - 02/2019]

      HINT: 

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

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  6

  6. CHECK DTC 
    1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
    2. Turn the ignition switch to ON, and wait for at least 60 seconds.
    3. Clear the DTCs stored in the occupant detection ECU.

      Refer to DTC CHECK / CLEAR [11/2018 - ]

      Body Electrical > Occupant Detection > Clear DTCs 

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

      Refer to DTC CHECK / CLEAR [11/2018 - ]

      Body Electrical > SRS Airbag > Clear DTCs 

    5. Turn the ignition switch off.
    6. Turn the ignition switch to ON, and wait for at least 60 seconds.
    7. Check the DTCs stored in the occupant detection ECU.

      Refer to DTC CHECK / CLEAR [11/2018 - ]

      Body Electrical > Occupant Detection > Trouble Codes 

      Result

      Proceed to
      DTC B1771 is not output
      DTC B1771 is output

      HINT: 

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

    Result: 

    DTC B1771 is not output 

    END (FRONT SEAT INNER BELT ASSEMBLY RH WAS DEFECTIVE) 

    Result: 

    DTC B1771 is output 

    See step  7

  7. REPLACE OCCUPANT DETECTION ECU 
    1. Turn the ignition switch off.
    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    3. Replace the occupant detection ECU with a new one.

      Refer to REMOVAL [11/2018 - 02/2019]

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

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  8

  8. PERFORM ZERO POINT CALIBRATION 
    1. Using the Techstream, perform "Zero Point Calibration".

      Refer to INITIALIZATION [11/2018 - ]

      Body Electrical > Occupant Detection > Utility 

      Tester Display
      Zero Point Calibration

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    END (OCCUPANT DETECTION ECU WAS DEFECTIVE) 

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