OCCUPANT CLASSIFICATION SYSTEM, Diagnostic DTC:B1781

DTC Code DTC Name
B1781 Front Occupant Classification Sensor RH Circuit Malfunction

DESCRIPTION

The front occupant classification sensor RH circuit consists of the occupant classification ECU and front occupant classification sensor RH.

DTC B1781 is recorded when a malfunction is detected in the front occupant classification sensor RH circuit.

DTC No. DTC Detection Condition Trouble Area
B1781

  • The occupant classification 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 front occupant classification sensor RH circuit for 2 seconds.

  • Front occupant classification sensor RH malfunction

  • Occupant classification ECU malfunction

  • Front seat frame with adjuster assembly RH (Front occupant classification sensor RH)

  • Occupant classification ECU

  • Front seat wire RH

Tech Tips

When DTC B1650/32 is detected as a result of troubleshooting for the airbag system, check the DTCs stored in the occupant classification ECU. When DTC B1781 is output, perform troubleshooting for the DTC.

WIRING DIAGRAM

A01ELREE06

INSPECTION PROCEDURE

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, 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 classification ECU and front occupant classification sensor 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 classification ECU and front occupant classification sensor RH.

    5. Check that the terminals of 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. A01ELQQE14
      Text in Illustration
      *1 Front Occupant Classification Sensor RH
      *2 Occupant Classification ECU
      *3 Front Seat Wire RH
      *4

      Front view of wire harness connector

      (to Occupant Classification ECU)
      *5 Connector B

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

    2. Turn the ignition switch to ON.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      S13-2 (SGD2) - Body ground Ignition switch ON Below 1 V
      S13-8 (SIG2) - Body ground Ignition switch ON Below 1 V
      S13-12 (SVC2) - Body ground Ignition switch ON Below 1 V

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  3. CHECK FRONT SEAT WIRE RH (OPEN)


    1. Turn the ignition switch off.

      A01EKZNE23

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

    3. Using SST, connect terminals 1 (SVC2) and 3 (SGD2), and connect terminals 2 (SIG2) and 3 (SGD2) of connector C.

      Note

      Do not forcibly insert SST into the terminals of the connector when connecting.

      SST
      09843-18040

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      S13-8 (SIG2) - S13-2 (SGD2) Always Below 1 Ω
      S13-12 (SVC2) - S13-2 (SGD2) Always Below 1 Ω
      Text in Illustration
      *1 Front Occupant Classification Sensor RH *2 Occupant Classification ECU
      *3 Front Seat Wire RH *4

      Front view of wire harness connector

      (to Occupant Classification ECU)
      *5

      Front view of wire harness connector

      (to Front Occupant Classification Sensor RH)

      		 *6 Connector B
      *7 Connector C - -

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  4. CHECK FRONT SEAT WIRE RH (SHORT)


    1. A01ELQQE14
      Text in Illustration
      *1 Front Occupant Classification Sensor RH
      *2 Occupant Classification ECU
      *3 Front Seat Wire RH
      *4

      Front view of wire harness connector

      (to Occupant Classification ECU)
      *5 Connector B

      Disconnect SST from connector C.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      S13-8 (SIG2) - S13-2 (SGD2) Always 1 MΩ or higher
      S13-12 (SVC2) - S13-2 (SGD2) Always 1 MΩ or higher
      S13-8 (SIG2) - S13-12 (SVC2) Always 1 MΩ or higher

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

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


    1. A01ELQQE14
      Text in Illustration
      *1 Front Occupant Classification Sensor RH
      *2 Occupant Classification ECU
      *3 Front Seat Wire RH
      *4

      Front view of wire harness connector

      (to Occupant Classification ECU)
      *5 Connector B

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      S13-2 (SGD2) - Body ground Always 1 MΩ or higher
      S13-8 (SIG2) - Body ground Always 1 MΩ or higher
      S13-12 (SVC2) - Body ground Always 1 MΩ or higher

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  6. CHECK DTC


    1. Connect the connectors to the occupant classification ECU and the front occupant classification sensor RH.

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

    3. Turn the ignition switch to ON.

    4. Clear the DTCs stored in the occupant classification ECU Click here.

    5. Clear the DTCs stored in the center 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 B1781 is not output.

      Tech Tips

      Codes other than DTC B1781 may be output at this time, but they are not related to this check.


    NG

    REPLACE OCCUPANT CLASSIFICATION ECU Click here

    OK

    USE SIMULATION METHOD TO CHECK Click here

  7. REPLACE OCCUPANT CLASSIFICATION ECU


    1. Turn the ignition switch off.

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

    3. Replace the occupant classification ECU Click here.

      Tech Tips

      Perform the inspection using parts from a normal vehicle if possible.


    NEXT

  8. PERFORM ZERO POINT CALIBRATION


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

    2. Connect the GTS to the DLC3.

    3. Turn the ignition switch to ON.

    4. Using the GTS, perform Zero Point Calibration Click here.

      OK
      "Zero Point Calibration is complete." is displayed.

    NG

    REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH Click here

    OK

  9. PERFORM SENSITIVITY CHECK


    1. Using the GTS, perform Sensitivity Check Click here.

      Standard
      27 to 33 kg (59.5 to 72.8 lb)

    NG

    REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH Click here

    OK

  10. CHECK DTC


    1. Turn the ignition switch to ON.

    2. Clear the DTCs stored in the occupant classification ECU Click here.

    3. Clear the DTCs stored in the center airbag sensor assembly Click here.

    4. Turn the ignition switch off.

    5. Turn the ignition switch to ON.

    6. Check for DTCs Click here.

      OK
      DTC B1781 is not output.

      Tech Tips

      Codes other than DTC B1781 may be output at this time, but they are not related to this check.


    NG

    REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH Click here

    OK

    END

  11. REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH


    1. Turn the ignition switch off.

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

    3. Replace the front seat frame with adjuster assembly RH Click here.


    NEXT

  12. PERFORM ZERO POINT CALIBRATION


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

    2. Connect the GTS to the DLC3.

    3. Turn the ignition switch to ON.

    4. Using the GTS, perform Zero Point Calibration Click here.

      OK
      "Zero Point Calibration is complete." is displayed.

    NEXT

  13. PERFORM SENSITIVITY CHECK


    1. Using the GTS, perform Sensitivity Check Click here.

      Standard
      27 to 33 kg (59.5 to 72.8 lb)

    NEXT

    END