OCCUPANT CLASSIFICATION SYSTEM, Diagnostic DTC:B1771

DTC Code DTC Name
B1771 Passenger Side Buckle Switch Circuit Malfunction

DESCRIPTION

The passenger side buckle switch circuit consists of the occupant detection ECU and passenger side buckle switch (front seat inner belt assembly RH).

DTC B1771 is stored when a malfunction is detected in the passenger side buckle switch circuit.

DTC No. Detection Item DTC Detection Condition Trouble Area
B1771 Passenger Side Buckle Switch Circuit Malfunction

  • The occupant detection ECU detects a line short, short to ground or B+, or an open in the passenger side buckle switch circuit.

  • Passenger side buckle switch malfunction

  • Occupant detection ECU malfunction

  • Front seat wire RH

  • Passenger side buckle switch (Front seat inner belt assembly RH)

  • Occupant detection ECU

WIRING DIAGRAM

B004P42E17
*a BSW
*b Passenger Side Buckle Switch (Front Seat Inner Belt Assembly RH)
*c Occupant Detection ECU

CAUTION / NOTICE / HINT

Note

After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.

Click here

Tech Tips


  • When DTC B1650/32 is stored as a result of troubleshooting for the airbag system, check the DTCs stored in the occupant detection ECU. When DTC B1771 is output, perform troubleshooting for this DTC first.

  • If it is difficult to perform troubleshooting (wire harness inspection), remove the front passenger seat installation bolts to see under the seat cushion.

  • In the above case, lift and hold the seat so that it does not fall down. Hold the seat only as necessary because holding the seat for a long period of time may cause seat rail deformation.

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.

      Tech Tips

      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

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  2. CHECK FRONT SEAT WIRE RH (SHORT TO B+)


    1. B004OV6C06
      *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)

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

    2. Turn the power switch on (IG).

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      a11-7 (BSW) - Body ground Power switch on (IG) Below 1 V
      a11-9 (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

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  3. CHECK FRONT SEAT WIRE RH (OPEN)


    1. B004QZXC07
      *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)

      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.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      a11-7 (BSW) - a11-9 (BGND) Always Below 1 Ω

    3. Disconnect the service wire from connector C.

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  4. CHECK FRONT SEAT WIRE RH (SHORT)


    1. B004OV6C06
      *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)

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      a11-7 (BSW) - a11-9 (BGND) Always 1 MΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  5. CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)


    1. B004OV6C06
      *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)

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      a11-7 (BSW) - Body ground Always 1 MΩ or higher
      a11-9 (BGND) - Body ground Always 1 MΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  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.

      Click here


      Body Electrical > Occupant Detection > Clear DTCs

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

      Click here


      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.

      Click here


      Body Electrical > Occupant Detection > Trouble Codes
      OK
      DTC B1771 is not output.

      Tech Tips

      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

    OK

    USE SIMULATION METHOD TO CHECK Click here

    NG

  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.

      Click here

      Tech Tips

      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.

      Click here


      Body Electrical > Occupant Detection > Clear DTCs

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

      Click here


      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.

      Click here


      Body Electrical > Occupant Detection > Trouble Codes
      OK
      DTC B1771 is not output.

      Tech Tips

      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.

      Click here

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE FRONT SEAT INNER BELT ASSEMBLY RH Click here

    NG

  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.

      Click here

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

      Result
      Proceed to
      NEXT

    NEXT

  9. PERFORM ZERO POINT CALIBRATION


    1. Using the GTS, perform Zero Point Calibration.

      Click here


      Body Electrical > Occupant Detection > Utility
      Tester Display
      Zero Point Calibration
      Result
      Proceed to
      NEXT

    NEXT

    END