OCCUPANT CLASSIFICATION SYSTEM (for TMMK Made), Diagnostic DTC:B1793

DTC Code DTC Name
B1793 Occupant Classification Sensor Power Supply Circuit Malfunction

DESCRIPTION

The occupant classification sensor power supply circuit consists of the occupant detection ECU, front occupant classification sensor LH and rear occupant classification sensor LH.

DTC B1793 is stored when a malfunction is detected in the occupant classification sensor power supply circuit.

DTC No. DTC Detection Condition Trouble Area
B1793

  • The occupant detection ECU detects a line short, or short to ground or B+ in the occupant classification sensor power supply circuit.

  • Front occupant classification sensor LH malfunction

  • Rear occupant classification sensor LH malfunction

  • Occupant detection ECU malfunction

  • Front seat wire RH

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

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

  • Occupant detection ECU

WIRING DIAGRAM

B000M05E02

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 B1793 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 front occupant classification sensor LH, rear occupant classification sensor LH and occupant detection ECU.

      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 front occupant classification sensor LH, rear occupant classification sensor LH and occupant detection ECU.

    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. B000NGXE09
      Text in Illustration
      *1 Front Occupant Classification Sensor LH
      *2 Rear Occupant Classification Sensor LH
      *3 Occupant Detection ECU
      *4 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
      d8-1 (SVC1) - Body ground Engine switch on (IG) Below 1 V
      d8-2 (SVC3) - 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 FRAME WITH ADJUSTER ASSEMBLY RH Click here

    OK

  3. CHECK FRONT SEAT WIRE RH (SHORT)


    1. B000NGXE09
      Text in Illustration
      *1 Front Occupant Classification Sensor LH
      *2 Rear Occupant Classification Sensor LH
      *3 Occupant Detection ECU
      *4 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
      d8-1 (SVC1) - d8-2 (SVC3) Always 1 MΩ or higher

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

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


    1. B000NGXE09
      Text in Illustration
      *1 Front Occupant Classification Sensor LH
      *2 Rear Occupant Classification Sensor LH
      *3 Occupant Detection ECU
      *4 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
      d8-1 (SVC1) - Body ground Always 1 MΩ or higher
      d8-2 (SVC3) - Body ground Always 1 MΩ or higher

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

  5. CHECK DTC


    1. Connect the connectors to the occupant detection ECU, front occupant classification sensor LH and rear occupant classification sensor LH.

    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 B1793 is not output.

      Tech Tips

      Codes other than DTC B1793 may be output at this time, but they are not related to this check.

    8. Turn the engine switch off.


    NG

    CHECK OCCUPANT DETECTION ECU Click here

    OK

    USE SIMULATION METHOD TO CHECK Click here

  6. CHECK OCCUPANT DETECTION ECU


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

    2. Replace the occupant detection ECU 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 B1793 is not output.

      Tech Tips

      Codes other than DTC B1793 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 occupant detection ECU that was installed for testing to its original location Click here.


    NG

    REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH Click here

    OK

  7. 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

  8. PERFORM ZERO POINT CALIBRATION AND SENSITIVITY CHECK


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


    NEXT

    END

  9. REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH


    1. Turn the engine switch off.

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

    3. Replace the front seat frame with adjuster assembly RH Click here for Manual Seat, Click here for Power Seat).

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


    NEXT

  10. PERFORM ZERO POINT CALIBRATION AND SENSITIVITY CHECK


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


    NEXT

    END

  11. REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH


    1. Replace the front seat frame with adjuster assembly RH Click here for Manual Seat, Click here for Power Seat).

      Note

      Replace the front seat wire RH at the same time.

      Tech Tips

      When the front seat wire RH has a short to B+, the front occupant classification sensor LH or rear occupant classification sensor LH will be damaged. Therefore, replace the front seat wire RH and the front seat frame with adjuster assembly RH, which includes the front occupant classification sensor LH and rear occupant classification sensor LH.

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


    NEXT

  12. PERFORM ZERO POINT CALIBRATION AND SENSITIVITY CHECK


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


    NEXT

    END