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Home >> Lexus >> 2009 >> GX 470 >> Repair and Diagnosis (Single Page) >> Restraints >> Air Bag, SRS >> Occupant Classification System (Diagnostic Codes & Symptom Tests) >> Occupant Classification System >> DTC B1793: Occupant Classification Sensor Power Supply Circuit Malfunction >> Procedure

DTC B1793: Occupant Classification Sensor Power Supply Circuit Malfunction: Procedure

  1. CHECK DTC 
    1. Turn the ignition switch to the ON position.
    2. Clear the 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 assembly.

    3. Turn the ignition switch to the LOCK position.
    4. Turn the ignition switch to the ON position.
    5. Check the DTCs. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1793 is not output.

      HINT: 

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

    OK → USE SIMULATION METHOD TO CHECK 

    NG: Go to next step 

  2. CHECK CONNECTION OF CONNECTORS 
    1. Turn the ignition switch to the LOCK position.
    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 occupant classification sensors.

      OK

      The connectors are properly connected.

    NG → CONNECT CONNECTORS, THEN GO TO STEP 1 

    OK: Go to next step 

  3. CHECK SEAT WIRE NO. 1 (SHORT TO B+) 
    1. Disconnect the connectors from the occupant classification ECU and the 4 occupant classification sensors.
      Fig 1: Identifying O4 Occupant Classification Sensors ECU Connector Terminals
      GTY155687Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Connect the negative (-) terminal cable to the battery.
    3. Turn the ignition switch to the ON position.
    4. Measure the voltage according to the value(s) in the table below.

      Standard voltage

      Tester connection Condition Specified condition
      O4-5 (SVC3) - Body ground Ignition switch ON Below 1 V
      O4-6 (SVC4) - Body ground Ignition switch ON Below 1 V
      O4-11 (SVC1) - Body ground Ignition switch ON Below 1 V
      O4-12 (SVC2) - Body ground Ignition switch ON Below 1 V

    NG → REPAIR OR REPLACE SEAT WIRE NO. 1 

    OK: Go to next step 

  4. CHECK SEAT WIRE NO. 1 (SHORT TO GROUND) 
    1. Turn the ignition switch to the LOCK position.
      Fig 2: Identifying O4 Occupant Classification Sensors ECU Connector Terminals
      GTY155688Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester connection Condition Specified condition
      O4-5 (SVC3) - Body ground Always 1 MΩ or higher
      O4-6 (SVC4) - Body ground Always 1 MΩ or higher
      O4-11 (SVC1) - Body ground Always 1 MΩ or higher
      O4-12 (SVC2) - Body ground Always 1 MΩ or higher

    NG → REPAIR OR REPLACE SEAT WIRE NO. 1 

    OK: Go to next step 

  5. CHECK SEAT WIRE NO. 1 (OPEN) 
    1. Measure the resistance according to the value(s) in the table below.
      Fig 3: Identifying O4 Occupant Classification Sensors ECU Connector Terminals
      GTY155689Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard resistance

      Tester connection Condition Specified condition
      O4-5 (SVC3) - O7-1 (SVC3) Always Below 1 Ω
      O4-6 (SVC4) - O8- 1 (SVC4) Always Below 1 Ω
      O4-11 (SVC1) - O5-1 (SVC1) Always Below 1 Ω
      O4-12 (SVC2) - O6-1 (SVC2) Always Below 1 Ω

    NG → REPAIR OR REPLACE SEAT WIRE NO. 1 

    OK: Go to next step 

  6. CHECK SEAT WIRE NO. 1 (SHORT) 
    1. Measure the resistance according to the value(s) in the table below.
      Fig 4: Identifying O4 Occupant Classification Sensors ECU Connector Terminals
      GTY121230Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard resistance

      Tester connection Condition Specified condition
      O4-5 (SVC3) - O4-6 (SVC4) Always 1 MΩ or higher
      O4-6 (SVC4) - O4-11 (SVC1) Always 1 MΩ or higher
      O4-11 (SVC1) - O4-12 (SVC2) Always 1 MΩ or higher
      O4-12 (SVC2) - O4-5 (SVC3) Always 1 MΩ or higher
      O4-12 (SVC2) - O4-6 (SVC4) Always 1 MΩ or higher
      O4-11 (SVC1) - O4-5 (SVC3) Always 1 MΩ or higher

    NG → REPAIR OR REPLACE SEAT WIRE NO. 1 

    OK: Go to next step 

  7. CHECK DTC 
    1. Connect the connectors to the occupant classification ECU and the 4 occupant classification sensors.
    2. Connect the negative (-) terminal cable to the battery.
    3. Turn the ignition switch to the ON position.
    4. Clear the 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 assembly.

    5. Turn the ignition switch to the LOCK position.
    6. Turn the ignition switch to the ON position.
    7. Check the DTCs. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1793 is not output.

      HINT: 

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

    OK → USE SIMULATION METHOD TO CHECK 

    NG: Go to next step 

  8. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Turn the ignition switch to the LOCK position.
    2. Disconnect the negative (-) terminal cable from the battery.
    3. Replace the occupant classification ECU. Refer to REMOVAL .

      HINT: 

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

    NEXT: Go to next step 

  9. PERFORM ZERO POINT CALIBRATION 
    1. Connect the negative (-) terminal cable to the battery.
    2. Connect the Techstream to the DLC3.
    3. Turn the ignition switch to the ON position.
    4. Using the Techstream, perform "Zero point calibration". Refer to INITIALIZATION .

      OK

      "Zero Point Calibration is complete." is displayed.

    NG → See step   12 

    OK: Go to next step 

  10. PERFORM SENSITIVITY CHECK 
    1. Using the Techstream, perform "Sensitivity check". Refer to INITIALIZATION .

      Standard value

      27 to 33 kg (59.52 to 72.75 lb)

    NG → See step   12 

    OK: Go to next step 

  11. CHECK DTC 
    1. Connect the negative (-) terminal cable to the battery.
    2. Turn the ignition switch to the ON position.
    3. Clear the 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 assembly.

    4. Turn the ignition switch to the LOCK position.
    5. Turn the ignition switch to the ON position.
    6. Check the DTCs. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1793 is not output.

      HINT: 

      Codes other than DTC B1793 may be output at this time, but they are related to this check.

    OK → END 

    NG: Go to next step 

  12. REPLACE FRONT SEAT WITH ADJUSTER FRAME ASSEMBLY RH 
    1. Turn the ignition switch to the LOCK position.
    2. Disconnect the negative (-) terminal cable from the battery.
    3. Replace the front seat with adjuster frame assembly RH. Refer to REMOVAL .

    NEXT: Go to next step 

  13. PERFORM ZERO POINT CALIBRATION 
    1. Connect the negative (-) terminal cable to the battery.
    2. Connect the Techstream to the DLC3.
    3. Turn the ignition switch to the ON position.
    4. Using the Techstream, perform "Zero point calibration". Refer to INITIALIZATION .

      OK

      "Zero Point Calibration is complete." is displayed.

    NEXT: Go to next step 

  14. PERFORM SENSITIVITY CHECK 
    1. Using the Techstream, perform "Sensitivity check". Refer to INITIALIZATION .

      Standard value

      27 to 33 kg (59.52 to 72.75 lb)

    NEXT → END 

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