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 front seat inner belt assembly RH.

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

DTC No. DTC Detection Condition Trouble Area
B1771

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

  • Passenger side buckle switch malfunction

  • Occupant detection ECU malfunction

  • Front seat wire RH

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

  • Occupant detection ECU

Tech Tips

When DTC B1650/32 is detected 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 the DTC.

WIRING DIAGRAM

A011V1CE01

INSPECTION PROCEDURE

Note

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

Tech Tips

  • If troubleshooting (wire harness inspection) is difficult to perform, 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 ignition 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.

      Tech Tips

      If the connectors are not connected securely, 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 damaged.

      OK
      The terminals are not deformed or damaged.
    NG

    REPLACE FRONT SEAT WIRE RH

    OK

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

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

      A011UYVE02

    2. Turn the ignition switch to ON.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      d11-8 (BSW) - Body ground Ignition switch ON Below 1 V
      d11-5 (BGND) - Body ground Ignition switch ON Below 1 V

    4. Turn the ignition switch off.

    5. Disconnect the cable from the negative (-) battery terminal.

      Text in Illustration
      *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)
    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  3. CHECK FRONT SEAT WIRE RH (OPEN)

    1. Using a service wire, connect terminals BSW and BGND of connector C as shown in the illustration.

      A011RHNE02

      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
      d11-8 (BSW) - d11-5 (BGND) Always Below 1 Ω

    3. Disconnect the service wire from connector C.

      Text in Illustration
      *A for TMMK Made Manual Seat
      *B for TMMK Made Power Seat
      *C for SIA Made
      *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)
    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  4. CHECK FRONT SEAT WIRE RH (SHORT)

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

      A011UYVE02
      Standard Resistance
      Tester Connection Condition Specified Condition
      d11-8 (BSW) - d11-5 (BGND) Always 1 MΩ or higher
      Text in Illustration
      *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)
    NG

    REPLACE FRONT SEAT WIRE RH

    OK

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

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

      A011UYVE02
      Standard Resistance
      Tester Connection Condition Specified Condition
      d11-8 (BSW) - Body ground Always 1 MΩ or higher
      d11-5 (BGND) - Body ground Always 1 MΩ or higher
      Text in Illustration
      *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)
    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 (-) battery terminal.

    3. Clear the DTCs stored in the occupant detection ECU Click here.

    4. Clear the DTCs stored in the airbag sensor assembly Click here.

    5. Turn the ignition switch off.

    6. Turn the ignition switch to ON.

    7. Check for DTCs Click here.

      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 ignition switch off.

    NG

    CHECK FRONT SEAT INNER BELT ASSEMBLY RH Click here

    OK

    USE SIMULATION METHOD TO CHECK Click here

  7. CHECK FRONT SEAT INNER BELT ASSEMBLY RH

    1. Disconnect the cable from the negative (-) battery terminal.

    2. Replace the front seat inner belt assembly RH with a known good one Click here for Manual Seat, Click here for Power Seat).

      Tech Tips

      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 Click here.

    5. Clear the DTCs stored in the airbag sensor assembly Click here.

    6. Turn the ignition switch off.

    7. Turn the ignition switch to ON.

    8. Check for DTCs Click here.

      OK
      DTC B1771 is not output.
      Result
      Result Proceed to
      OK (for Manual Seat) A
      OK (for Power Seat) B
      NG C

      Tech Tips

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

    9. Turn the ignition 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 Click here for Manual Seat, Click here for Power Seat).

    B

    REPLACE FRONT SEAT INNER BELT ASSEMBLY RH Click here

    C

    REPLACE OCCUPANT DETECTION ECU Click here

    A

    REPLACE FRONT SEAT INNER BELT ASSEMBLY RH Click here

  8. REPLACE OCCUPANT DETECTION ECU

    1. Disconnect the cable from the negative (-) battery terminal.

    2. Replace the occupant detection ECU with a new one Click here.

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

    NEXT

  9. PERFORM ZERO POINT CALIBRATION AND SENSITIVITY CHECK

    1. Using the Techstream, perform Zero Point Calibration and Sensitivity Check Click here.

    NEXT

    END