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DTC B1771: Passenger Side Buckle Switch Circuit Malfunction [10/2014 - 05/2019]: Procedure

  1. CHECK DTC 
    1. Turn the engine switch on (IG), and wait for at least 60 seconds.
    2. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [10/2014 - ]

      Body Electrical > Occupant Detection > Clear DTCs 

      HINT: 

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

    3. Turn the engine switch off.
    4. Turn the engine switch on (IG), and wait for at least 60 seconds.
    5. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2014 - ]

      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 

    USE SIMULATION METHOD TO CHECK. Refer to  DIAGNOSIS SYSTEM [10/2014 - ] 

    Result: 

    DTC B1771 is output 

    See step  2

  2. CHECK CONNECTION OF CONNECTORS 
    1. Turn the engine 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.

      Result

      Proceed to
      Connectors are properly connected
      Connectors are not properly connected

    Result: 

    Connectors are not properly connected 

    CONNECT CONNECTORS 

    Result: 

    Connectors are properly connected 

    See step  3

  3. CHECK CONNECTORS 
    1. Disconnect the connectors from the occupant detection ECU and the front seat inner belt assembly RH.
      GTY374349Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Front Seat Inner Belt Assembly RH
      *2 Occupant Detection ECU
      *3 Front Seat Wire RH
    2. Check that the connectors (on the occupant detection ECU side and the 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 

    Result: 

    Connectors are not deformed or damaged 

    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 engine switch on (IG), and wait for at least 60 seconds.
    4. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [10/2014 - ]

      Body Electrical > Occupant Detection > Clear DTCs 

      HINT: 

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

    5. Turn the engine switch off.
    6. Turn the engine switch on (IG), and wait for at least 60 seconds.
    7. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2014 - ]

      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 

    USE SIMULATION METHOD TO CHECK. Refer to  DIAGNOSIS SYSTEM [10/2014 - ] 

    Result: 

    DTC B1771 is output 

    See step  5

  5. CHECK FRONT SEAT WIRE RH 
    GTY513407Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    *1 Front Seat Inner Belt Assembly RH *2 Occupant Detection ECU
    *3 Front Seat Wire RH *4 Connector B
    *5 Connector C *6 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)
    1. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      f15-8 (BSW) - Body ground Engine switch on (IG) Below 1 V
      f15-5 (BGND) - Body ground
    2. Turn the engine switch off.
    3. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    4. Using service wires, connect terminals 1 (+) and 2 (-) of connector C.
      NOTE:

      Do not forcibly insert the service wires into the terminals of the connector.

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      f15-8 (BSW) - f15-5 (BGND) Always Below 1 Ω
    6. Disconnect the service wires from connector C.
    7. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      f15-8 (BSW) - f15-5 (BGND) Always 1 MΩ or higher
      f15-8 (BSW) - Body ground
      f15-5 (BGND) - Body ground

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result: 

    OK 

    See step  6

  6. CHECK FRONT SEAT INNER BELT ASSEMBLY RH 
    1. Replace the front seat inner belt assembly RH.

      Refer to REMOVAL [10/2014 - ]

      HINT: 

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

    2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
    3. Turn the engine switch on (IG), and wait for at least 60 seconds.
    4. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [10/2014 - ]

      Body Electrical > Occupant Detection > Clear DTCs 

      HINT: 

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

    5. Turn the engine switch off.
    6. Turn the engine switch on (IG), and wait for at least 60 seconds.
    7. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2014 - ]

      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 engine switch off.
    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    3. Replace the occupant detection ECU.

      Refer to REMOVAL [10/2014 - 05/2019]

      HINT: 

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

    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. Perform the zero point calibration.

      Refer to INITIALIZATION [10/2014 - ]

      Result

      Proceed to
      "Zero Point Calibration is complete." is displayed

    Result: 

    "Zero Point Calibration is complete." is displayed 

    See step  9

  9. PERFORM SENSITIVITY CHECK 
    1. Perform the sensitivity check.

      Refer to INITIALIZATION [10/2014 - ]

      Standard

      27 to 33 kg (59.5 to 72.8 lb)

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    END (OCCUPANT DETECTION ECU WAS DEFECTIVE) 

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