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DTC B1771: Passenger Side Buckle Switch Circuit Malfunction [11/2015 - 12/2018]: Procedure

  1. CHECK CONNECTORS 
    1. Turn the power switch off.
    2. Disconnect the cable from the negative (-) auxiliary 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

  2. CHECK FRONT SEAT WIRE RH (SHORT TO B+) 
    1. Connect the cable to the negative (-) auxiliary battery terminal.
      GTY591102Courtesy 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)
    2. Turn the power switch on (IG).
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      (a8)

      (a8)

      Tester Connection Condition Specified Condition
      a8-7 (BSW) - Body ground Power switch on (IG) Below 1 V
      a8-9 (BGND) - Body ground Power switch on (IG) Below 1 V
    4. Turn the power switch off.
    5. Disconnect the cable from the negative (-) auxiliary battery terminal.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result: 

    OK 

    See step  3

  3. CHECK FRONT SEAT WIRE RH (OPEN) 
    1. Using a service wire, connect terminals 1 (+) and 2 (-) of connector C.
      GTY598764Courtesy 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.

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

      Standard Resistance

      (a8)

      (a8)

      Tester Connection Condition Specified Condition
      a8-7 (BSW) - a8-9 (BGND) Always Below 1 Ω
    3. Disconnect the service wire from connector C.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result: 

    OK 

    See step  4

  4. CHECK FRONT SEAT WIRE RH (SHORT) 
    1. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      (a8)

      (a8)

      Tester Connection Condition Specified Condition
      a8-7 (BSW) - a8-9 (BGND) Always 1 MΩ or higher
      GTY591102Courtesy 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: 

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result: 

    OK 

    See step  5

  5. CHECK FRONT SEAT WIRE RH (SHORT TO GROUND) 
    1. Measure the resistance according to the value(s) in the table below.
      GTY591102Courtesy 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

      (a8)

      (a8)

      Tester Connection Condition Specified Condition
      a8-7 (BSW) - Body ground Always 1 MΩ or higher
      a8-9 (BGND) - Body ground Always 1 MΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE FRONT SEAT WIRE RH 

    Result: 

    OK 

    See step  6

  6. 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 (-) auxiliary battery terminal.
    3. Clear the DTCs stored in the occupant detection ECU.

      Refer to DTC CHECK / CLEAR [11/2015 - ]

      Body Electrical > Occupant Detection > Clear DTCs 

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

      Refer to DTC CHECK / CLEAR [11/2015 - 12/2018]

      Body Electrical > SRS Airbag > Clear DTCs 

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

      Refer to DTC CHECK / CLEAR [11/2015 - ]

      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 power switch off.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2015 - 12/2018] 

    Result: 

    NG 

    See step  7

  7. CHECK FRONT SEAT INNER BELT ASSEMBLY RH 
    1. Disconnect the cable from the negative (-) auxiliary battery terminal.
    2. Replace the front seat inner belt assembly RH with a known good one.

      Refer to REMOVAL [11/2015 - 12/2018]

      HINT: 

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

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

      Refer to DTC CHECK / CLEAR [11/2015 - ]

      Body Electrical > Occupant Detection > Clear DTCs 

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

      Refer to DTC CHECK / CLEAR [11/2015 - 12/2018]

      Body Electrical > SRS Airbag > Clear DTCs 

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

      Refer to DTC CHECK / CLEAR [11/2015 - ]

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

      Refer to REMOVAL [11/2015 - 12/2018]

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE FRONT SEAT INNER BELT ASSEMBLY RH. Refer to  REMOVAL [11/2015 - 12/2018] 

    Result: 

    NG 

    See step  8

  8. REPLACE OCCUPANT DETECTION ECU 
    1. Turn the power switch off.
    2. Disconnect the cable from the negative (-) auxiliary battery terminal.
    3. Replace the occupant detection ECU with a new one.

      Refer to REMOVAL [11/2015 - 12/2018]

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

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  9

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

      Refer to INITIALIZATION [11/2015 - ]

      Body Electrical > Occupant Detection > Utility 

      Tester Display
      Zero Point Calibration

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    END 

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