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DTC B1781: Front Occupant Classification Sensor RH Circuit Malfunction: Procedure

  1. CHECK FOR DTC 
    1. Turn the ignition switch ON, and wait for at least 60 seconds.
    2. Clear any DTCs stored in the memory. Refer to DTC CHECK / CLEAR .

      HINT: 

      • First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.
      • Use a Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
    3. Turn the ignition switch off.
    4. Turn the ignition switch ON, and wait for at least 60 seconds.
    5. Using the Techstream, check for DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1781 is not output.

      HINT: 

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

    NG → See step   2 

    OK → See step   13 

  2. CHECK CONNECTION OF CONNECTOR 
    1. Turn the ignition switch off.
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Check that the connectors are properly connected to the occupant classification ECU and the front occupant classification sensor RH.

      OK

      Connectors are properly connected.

    NG → CONNECT CONNECTOR 

    OK: Go to next step 

  3. CHECK CONNECTOR 
    1. Check that the connectors (on the occupant classification ECU side and front occupant classification sensor RH side) are not damaged. Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE .

      OK

      Connectors are not deformed or damaged.

    NG → REPLACE FRONT SEAT WIRE RH 

    OK: Go to next step 

  4. CHECK FRONT SEAT WIRE RH 
    Fig 1: Measuring Voltage Of Z8 & Z11 Connectors
    GTY164433Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the connectors from the occupant classification ECU and the front occupant classification sensor RH.
    2. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
    3. Turn the ignition switch ON, and wait for at least 60 seconds.
    4. Measure the voltage according to the value(s) in the table below.

      Standard voltage

      Tester Connection Switch Condition Specified Condition
      z8-2 (SGD2) - Body ground Ignition switch ON Below 1 V
      z8-8 (SIG2) - Body ground
      z8-12 (SVC2) - Body ground
    5. Turn the ignition switch off.
    6. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    7. Using service wires, connect terminals 1 (SVC2) and 3 (SGD2), and connect terminals 2 (SIG2) and 3 (SGD2) of connector C.
      NOTE:

      Do not forcibly insert the service wires into the terminals of the connector.

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

      Standard resistance

      Tester Connection Condition Specified Condition
      z8-8 (SIG2) - z8-2 (SGD2) Always Below 1 Ω
      z8-12 (SVC2) - z8-2 (SGD2)
    9. Disconnect the service wires from connector C.
    10. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      z8-8 (SIG2) - z8-2 (SGD2) Always 1 MΩ or higher
      z8-12 (SVC2) - z8-2 (SGD2)
      z8-8 (SIG2) - z8-12 (SVC2)
      z8-2 (SGD2) - Body ground
      z8-8 (SIG2) - Body ground
      z8-12 (SVC2) - Body ground

    NG → REPLACE FRONT SEAT WIRE RH 

    OK: Go to next step 

  5. CHECK FOR DTC 
    1. Connect the connectors to the occupant classification ECU and the front occupant classification sensor RH.
    2. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
    3. Turn the ignition switch ON, and wait for at least 60 seconds.
    4. Clear any DTCs stored in the memory. Refer to DTC CHECK / CLEAR .

      HINT: 

      • First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.
      • Use a Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
    5. Turn the ignition switch off.
    6. Turn the ignition switch ON, and wait for at least 60 seconds.
    7. Using the Techstream, check for DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1781 is not output.

      HINT: 

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

    NG → See step   6 

    OK → See step   13 

  6. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Turn the ignition switch off.
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Replace the occupant classification ECU. Refer to REMOVAL .

      HINT: 

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

    NEXT: Go to next step 

  7. PERFORM ZERO POINT CALIBRATION 
    1. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
    2. Connect a Techstream to the DLC3.
    3. Turn the ignition switch ON, and wait for at least 60 seconds.
    4. Using the Techstream, perform the zero point calibration. Refer to INITIALIZATION .

    NG → See step   10 

    OK: Go to next step 

  8. PERFORM SENSITIVITY CHECK 
    1. Using a Techstream, perform the sensitivity check. Refer to INITIALIZATION .

      Standard range

      27 to 33 kg (59.5 to 72.8 lb)

    NG → See step   10 

    OK: Go to next step 

  9. CHECK FOR DTC 
    1. Turn the ignition switch ON, and wait for at least 60 seconds.
    2. Clear any DTCs stored in the memory. Refer to DTC CHECK / CLEAR .

      HINT: 

      • First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.
      • Use a Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
    3. Turn the ignition switch off.
    4. Turn the ignition switch ON, and wait for at least 60 seconds.
    5. Using the Techstream, check for DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1781 is not output.

      HINT: 

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

    NG → See step   10 

    OK → END 

  10. REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH 
    1. Turn the ignition switch off.
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Replace the front seat frame with adjuster RH. Refer to DISASSEMBLY .

      HINT: 

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

    NEXT: Go to next step 

  11. PERFORM ZERO POINT CALIBRATION 
    1. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
    2. Connect a Techstream to the DLC3.
    3. Turn the ignition switch ON, and wait for at least 60 seconds.
    4. Using the Techstream, perform the zero point calibration. Refer to INITIALIZATION .

    NEXT: Go to next step 

  12. PERFORM SENSITIVITY CHECK 
    1. Using a Techstream, perform the sensitivity check. Refer to INITIALIZATION .

      Standard range

      27 to 33 kg (59.5 to 72.8 lb)

    NEXT → END 

  13. USE SIMULATION METHOD TO CHECK. Refer to  DIAGNOSIS SYSTEM 
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