OCCUPANT CLASSIFICATION SYSTEM, Diagnostic DTC:B1771

DTC Code DTC Name
B1771 Passenger Side Buckle Switch Circuit Malfunction

DESCRIPTION

The front passenger side buckle switch circuit consists of the occupant detection ECU and front seat inner belt assembly LH*1 and RH*2.

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

Troubleshoot DTC B1771 first when DTCs B1771 and B1795 are output simultaneously.

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

    One of the following conditions is met:

  • Occupant detection ECU detects a line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to +B signal in the front passenger side buckle switch circuit for 2 seconds.

  • Front passenger side buckle switch malfunction.

  • Occupant detection ECU malfunction.

  • Front seat wire RH

  • Front seat inner belt assembly LH*1

  • Front seat inner belt assembly RH*2

  • Occupant detection ECU

Tech Tips


  • When DTC B1650/32 is stored as a result of troubleshooting the airbag system, perform troubleshooting for DTC B1771 of the occupant classification system.

  • Use the GTS to check for DTCs of the occupant detection ECU, otherwise the DTCs cannot be read.

WIRING DIAGRAM

B0025GYE51

CAUTION / NOTICE / HINT

Note

When disconnecting the cable, some systems need to be initialized after the cable is reconnected.

Click here

Tech Tips


  • If troubleshooting (wire harness inspection) is difficult to perform, remove the front seat LH*1 and RH*2 installation bolts to see the undersurface of the seat cushion.

  • In the above case, hold the seat so that it does not fall down. Holding the seat for a long period of time may cause a problem, such as seat rail deformation. Hold the seat up only for as long as necessary.


    • *1: for RHD

    • *2: for LHD

PROCEDURE


  1. CHECK DTC


    1. Turn the ignition switch to ON, and wait for at least 60 seconds.

    2. Clear the DTCs.

      Click here


      Body Electrical > Occupant Detection > Clear DTCs

      Tech Tips

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

    3. Turn the ignition switch off.

    4. Turn the ignition switch to ON, and wait for at least 60 seconds.

    5. Check for DTCs.

      Click here


      Body Electrical > Occupant Detection > Trouble Codes
      Result
      Proceed to
      DTC B1771 is not output
      DTC B1771 is output

      Tech Tips

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


    DTC B1771 is not output

    USE SIMULATION METHOD TO CHECK Click here

    DTC B1771 is output

  2. CHECK CONNECTION OF CONNECTORS


    1. Turn the ignition 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

    Connectors are not properly connected

    CONNECT CONNECTORS

    Connectors are properly connected

  3. CHECK CONNECTORS


    1. B0026MKC03
      *A for RHD
      *B for LHD
      *1 Front Seat Inner Belt Assembly LH
      *2 Front Seat Inner Belt Assembly RH
      *3 Occupant Detection ECU
      *4 Front Seat Wire LH
      *5 Front Seat Wire RH

      Disconnect the connectors from the occupant detection ECU and the front seat inner belt assembly LH*1 and RH*2.

    2. Check that the connectors (on the occupant detection ECU side and the front seat inner belt assembly LH*1 and RH*2 side) are not damaged.


      • *1: for RHD

      • *2: for LHD

      Result
      Proceed to
      Connectors are not deformed or damaged
      Connectors are deformed or damaged (for RHD)
      Connectors are deformed or damaged (for LHD)

    Connectors are deformed or damaged (for RHD)

    REPLACE FRONT SEAT WIRE LH

    Connectors are deformed or damaged (for LHD)

    REPLACE FRONT SEAT WIRE RH

    Connectors are not deformed or damaged

  4. CHECK DTC


    1. Connect the connectors to the occupant detection ECU and front seat inner belt assembly LH*1 and RH*2.


      • *1: for RHD

      • *2: for LHD

    2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.

    3. Turn the ignition switch to ON, and wait for at least 60 seconds.

    4. Clear the DTCs.

      Click here


      Body Electrical > Occupant Detection > Clear DTCs

      Tech Tips

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

    5. Turn the ignition switch off.

    6. Turn the ignition switch to ON, and wait for at least 60 seconds.

    7. Check for DTCs.

      Click here


      Body Electrical > Occupant Detection > Trouble Codes
      Result
      Proceed to
      DTC B1771 is not output
      DTC B1771 is output (for RHD)
      DTC B1771 is output (for LHD)

      Tech Tips

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


    DTC B1771 is not output

    USE SIMULATION METHOD TO CHECK Click here

    DTC B1771 is output (for LHD)

    CHECK FRONT SEAT WIRE RH Click here

    DTC B1771 is output (for RHD)

  5. CHECK FRONT SEAT WIRE LH

    B0028YPC01
    *1 Front Seat Inner Belt Assembly LH *2 Occupant Detection ECU
    *3 Front Seat Wire LH *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 LH)

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      T10-9 (BSW) - Body ground Ignition switch ON Below 1 V
      T10-5 (BGND) - Body ground

    2. Turn the ignition 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
      T10-9 (BSW) - T10-5 (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
      T10-9 (BSW) - T10-5 (BGND) Always 1 MΩ or higher
      T10-9 (BSW) - Body ground
      T10-5 (BGND) - Body ground
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE FRONT SEAT WIRE LH

    OK

  6. CHECK FRONT SEAT INNER BELT ASSEMBLY LH


    1. Replace the front seat inner belt assembly LH.

      for Manual Seat: Click here

      for Power Seat: Click here

      Tech Tips

      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 ignition switch to ON, and wait for at least 60 seconds.

    4. Clear the DTCs.

      Click here


      Body Electrical > Occupant Detection > Clear DTCs

      Tech Tips

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

    5. Turn the ignition switch off.

    6. Turn the ignition switch to ON, and wait for at least 60 seconds.

    7. Check for DTCs.

      Click here


      Body Electrical > Occupant Detection > Trouble Codes
      Result
      Proceed to
      DTC B1771 is not output
      DTC B1771 is output

      Tech Tips

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


    DTC B1771 is not output

    END (FRONT SEAT INNER BELT ASSEMBLY LH WAS DEFECTIVE)

    DTC B1771 is output

  7. REPLACE OCCUPANT DETECTION ECU


    1. Turn the ignition switch off.

    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

    3. Replace the occupant detection ECU.

      Click here

      Tech Tips

      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

    NEXT

  8. PERFORM ZERO POINT CALIBRATION


    1. Perform the zero point calibration.

      Click here

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

    "Zero Point Calibration is complete." is displayed

  9. PERFORM SENSITIVITY CHECK


    1. Perform the sensitivity check.

      Click here

      Standard
      27 to 33 kg (59.5 to 72.8 lb)
      Result
      Proceed to
      NEXT

    NEXT

    END (OCCUPANT DETECTION ECU WAS DEFECTIVE)

  10. CHECK FRONT SEAT WIRE RH

    B0028YPC02
    *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
      S10-9 (BSW) - Body ground Ignition switch ON Below 1 V
      S10-5 (BGND) - Body ground

    2. Turn the ignition 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
      S10-9 (BSW) - S10-5 (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
      S10-9 (BSW) - S10-5 (BGND) Always 1 MΩ or higher
      S10-9 (BSW) - Body ground
      S10-5 (BGND) - Body ground
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  11. CHECK FRONT SEAT INNER BELT ASSEMBLY RH


    1. Replace the front seat inner belt assembly RH.

      for Manual Seat: Click here

      for Power Seat: Click here

      Tech Tips

      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 ignition switch to ON, and wait for at least 60 seconds.

    4. Clear the DTCs.

      Click here


      Body Electrical > Occupant Detection > Clear DTCs

      Tech Tips

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

    5. Turn the ignition switch off.

    6. Turn the ignition switch to ON, and wait for at least 60 seconds.

    7. Check for DTCs.

      Click here


      Body Electrical > Occupant Detection > Trouble Codes
      Result
      Proceed to
      DTC B1771 is not output
      DTC B1771 is output

      Tech Tips

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


    DTC B1771 is not output

    END (FRONT SEAT INNER BELT ASSEMBLY RH WAS DEFECTIVE)

    DTC B1771 is output

  12. REPLACE OCCUPANT DETECTION ECU


    1. Turn the ignition switch off.

    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

    3. Replace the occupant detection ECU.

      Click here

      Tech Tips

      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

    NEXT

  13. PERFORM ZERO POINT CALIBRATION


    1. Perform the zero point calibration.

      Click here

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

    "Zero Point Calibration is complete." is displayed

  14. PERFORM SENSITIVITY CHECK


    1. Perform the sensitivity check.

      Click here

      Standard
      27 to 33 kg (59.5 to 72.8 lb)
      Result
      Proceed to
      NEXT

    NEXT

    END (OCCUPANT DETECTION ECU WAS DEFECTIVE)