OCCUPANT CLASSIFICATION SYSTEM (for TMMK Made), 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 (passenger side buckle switch).

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 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

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

  • Occupant detection ECU

WIRING DIAGRAM

B000H4CE03

INSPECTION PROCEDURE

Note

After turning the engine 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


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

  • 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 engine 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. B000L7HE02
      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)

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

    2. Turn the engine switch on (IG).

    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 Engine switch on (IG) Below 1 V
      d11-5 (BGND) - Body ground Engine switch on (IG) Below 1 V

    4. Turn the engine switch off.

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


    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  3. CHECK FRONT SEAT WIRE RH (OPEN)


    1. B000K9XE01
      Text in Illustration
      *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 BSW and BGND of connector C as shown in the illustration.

      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.


    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  4. CHECK FRONT SEAT WIRE RH (SHORT)


    1. B000L7HE02
      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)

      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 1 MΩ or higher

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

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


    1. B000L7HE02
      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)

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

      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

    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 engine switch off.

    6. Turn the engine switch on (IG).

    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 engine 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.

      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 engine switch off.

    7. Turn the engine switch on (IG).

    8. 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.

    9. Turn the engine 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.


    NG

    REPLACE OCCUPANT DETECTION ECU Click here

    OK

    REPLACE FRONT SEAT INNER BELT ASSEMBLY RH Click here

  8. REPLACE OCCUPANT DETECTION ECU


    1. Turn the engine switch off.

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

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

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


    NEXT

  9. PERFORM ZERO POINT CALIBRATION AND SENSITIVITY CHECK


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


    NEXT

    END