LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2009 >> RX 350 AWD >> Repair and Diagnosis (Single Page) >> Restraints >> Air Bag, SRS >> Occupant Classification System (Diagnostic Codes & Symptom Tests) >> Occupant Classification System >> DTC B1780: Front Occupant Classification Sensor LH Circuit Malfunction >> Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC B1780: Front Occupant Classification Sensor LH Circuit Malfunction: Procedure

  1. CHECK DTC 
    1. Turn the ignition switch to the ON position.
    2. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
    3. Clear the DTCs stored in the center airbag sensor assembly. Refer to DTC CHECK / CLEAR .
    4. Turn the ignition switch to the ON position.
    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 B1780 is not output.

      HINT: 

      Codes other than DTC B1780 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 front occupant classification sensor LH.

      OK

      The connectors are properly connected.

    NG → CONNECT CONNECTOR PROPERLY, THEN GO TO STEP   1 

    OK: Go to next step 

  3. CHECK FRONT SEAT WIRE RH (SHORT TO B+) 
    1. Disconnect the connectors from the occupant classification ECU and the front occupant classification sensor LH.
      Fig 1: Checking Front Seat Wire RH (For A Short)
      GTY122319Courtesy 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
      O4-1 (SGD1) -
      Body ground      		 Ignition switch ON Below 1 V
      O4-7 (SIG1) -
      Body ground      		 Ignition switch ON Below 1 V
      O4-11 (SVC1) -
      Body ground      		 Ignition switch ON Below 1 V

    NG → REPAIR OR REPLACE FRONT SEAT WIRE RH 

    OK: Go to next step 

  4. CHECK FRONT SEAT WIRE RH (OPEN) 
    1. Turn the ignition switch to the LOCK position.
      Fig 2: Checking Front Seat Wire RH (Open)
      GTY113481Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Using a service wire, connect terminals 1 (SVC1) and 3 (SGD1), and connect terminals 2 (SIG1) and 3 (SGD1) of connector C.
      NOTE:

      Do not forcibly insert a service wire into the terminals of the connector when connecting.

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

      Standard resistance

      Tester Connection Condition Specified Condition
      O4-7 (SIG1) -
      O4-1 (SGD1)      		 Always Below 1 Ω
      O4-11 (SVC1) -
      O4-1 (SGD1)      		 Always Below 1 Ω

    NG → REPAIR OR REPLACE FRONT SEAT WIRE RH 

    OK: Go to next step 

  5. CHECK FRONT SEAT WIRE RH (SHORT) 
    1. Disconnect the service wire from connector C.
      Fig 3: Checking Front Seat Wire RH (For A Short)
      GTY122319Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      O4-7 (SIG1) -
      O4-1 (SGD1)      		 Always 1 MΩ or higher
      O4-11 (SVC1) -
      O4-1 (SGD1)      		 Always 1 MΩ or higher
      O4-7 (SIG1) -
      O4-11 (SVC1)      		 Always 1 MΩ or higher

    NG → REPAIR OR REPLACE FRONT SEAT WIRE RH 

    OK: Go to next step 

  6. CHECK FRONT SEAT WIRE RH (SHORT TO GROUND) 
    1. Measure the resistance according to the value(s) in the table below.
      Fig 4: Checking Front Seat Wire RH (For A Short)
      GTY122319Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard resistance

      Tester Connection Condition Specified Condition
      O4-1 (SGD1) -
      Body ground      		 Always 1 MΩ or higher
      O4-7 (SIG1) -
      Body ground      		 Always 1 MΩ or higher
      O4-11 (SVC1) -
      Body ground      		 Always 1 MΩ or higher

    NG → REPAIR OR REPLACE FRONT SEAT WIRE RH 

    OK: Go to next step 

  7. CHECK DTC 
    1. Connect the connectors to the occupant classification ECU and the front occupant classification sensor LH.
    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 occupant classification ECU. Refer to DTC CHECK / CLEAR .
    5. Clear the DTCs stored in the center airbag sensor assembly. Refer to DTC CHECK / CLEAR .
    6. Turn the ignition switch to the LOCK position.
    7. Turn the ignition switch to the ON position.
    8. Check the DTCs. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1780 is not output.

      HINT: 

      Codes other than DTC B1780 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, 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 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 values

      27 to 33 kg (59.52 to 72.75 lb)

    NG → See step   12 

    OK: Go to next step 

  11. CHECK DTC 
    1. Turn the ignition switch to the ON position.
    2. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
    3. Clear the DTCs stored in the center airbag sensor assembly. Refer to DTC CHECK / CLEAR .
    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 B1780 is not output.

      HINT: 

      Codes other than DTC B1780 may be output at this time, but they are not 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, and wait for at least 90 seconds.
    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 values

      27 to 33 kg (59.52 to 72.75 lb)

    NEXT → END 

scientia non olet · About LEMON Manuals