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DTC B1790: Center Airbag Sensor Assembly Communication Circuit Malfunction: Procedure

  1. CHECK FOR DTC 
    1. Turn the ignition switch to ON.
    2. Clear the DTCs.Refer to DTC CHECK / CLEAR .

      HINT: 

      First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.

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

      OK

      DTC B1790 is not output.

      HINT: 

      DTCs other than DTC B1790 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 CONNECTOR 
    1. Turn the ignition switch off.
    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    3. Check that the connectors are properly connected to the occupant classification ECU and the center airbag sensor.

      OK

      The connectors are properly connected.

    NG → CONNECT CONNECTOR 

    OK: Go to next step 

  3. CHECK FLOOR WIRE NO. 2 (TO B+) 
    1. Disconnect the connectors from the occupant classification ECU and the center airbag sensor.
      Fig 1: Checking Floor Wire No. 2 (To B+)
      GTY308694Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
    3. Turn the ignition switch to ON.
    4. Measure the voltage of the wire harness side connector.

      Standard voltage 

      W/ SIDE AIRBAG:

      Tester Connection Specified Condition
      L7-16 (FSP+) - Body ground Below 1 V
      L7-24 (FSP-) - Body ground Below 1 V
      W/O SIDE AIRBAG:

      Tester Connection Specified Condition
      L23-12 (FSP+) - Body ground Below 1 V
      L23-13 (FSP-) - Body ground Below 1 V

    NG → REPAIR OR REPLACE FLOOR WIRE NO. 2 

    OK: Go to next step 

  4. CHECK FLOOR WIRE NO. 2 (FOR OPEN) 
    1. Turn the ignition switch off.
      Fig 2: Checking Floor Wire No. 2 (For Open)
      GTY219043Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    3. Using a service wire, connect terminals L1-8 (FSR+) and L1-4 (FSR-) of connector C.
      NOTE:

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

    4. Measure the resistance of the wire harness side connector.

      Standard resistance 

      W/ SIDE AIRBAG:

      Tester Connection Specified Condition
      L7-16 (FSP+) - L7-24 (FSP-) Below 1 Ω
      W/O SIDE AIRBAG:

      Tester Connection Specified Condition
      L23-12 (FSP+) - L23-13 (FSP-) Below 1 Ω

    NG → REPAIR OR REPLACE FLOOR WIRE NO. 2 

    OK: Go to next step 

  5. CHECK FLOOR WIRE NO. 2 (FOR SHORT) 
    1. Disconnect the service wire from connector C.
      Fig 3: Checking Floor Wire No. 2 (For Short)
      GTY308694Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance of the wire harness side connector.

      Standard resistance 

      W/ SIDE AIRBAG:

      Tester Connection Specified Condition
      L7-16 (FSP+) - L7-24 (FSP-) 1 MΩ or higher
      W/O SIDE AIRBAG:

      Tester Connection Specified Condition
      L23-12 (FSP+) - L23-13 (FSP-) 1 MΩ or higher

    NG → REPAIR OR REPLACE FLOOR WIRE NO. 2 

    OK: Go to next step 

  6. CHECK FLOOR WIRE NO. 2 (TO GROUND) 
    Fig 4: Checking Floor Wire No. 2 (To Ground)
    GTY308694Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Measure the resistance of the wire harness side connector.

      Standard resistance 

      W/ SIDE AIRBAG:

      Tester Connection Specified Condition
      L7-16 (FSP+) - Body ground 1 MΩ or higher
      L7-24 (FSP-) - Body ground 1 MΩ or higher
      W/O SIDE AIRBAG:

      Tester Connection Specified Condition
      L23-12 (FSP+) - Body ground 1 MΩ or higher
      L23-13 (FSP-) - Body ground 1 MΩ or higher

    NG → REPAIR OR REPLACE FLOOR WIRE NO. 2 

    OK: Go to next step 

  7. CHECK FOR DTC 
    1. Connect the connectors to the occupant classification ECU and the center airbag sensor.
    2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
    3. Turn the ignition switch to ON.
    4. Clear the DTCs.Refer to DTC CHECK / CLEAR .

      HINT: 

      First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.

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

      OK

      DTC B1790 is not output.

      HINT: 

      DTCs other than DTC B1790 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 off.
    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    3. Replace the occupant classification ECU.Refer to COMPONENTS .

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

      OK

      "Zero Point Calibration is complete." is displayed.

    NEXT: Go to next step 

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

      Standard value 

      27 to 33 kg (59.52 to 72.75 lb)

    NEXT: Go to next step 

  11. CHECK FOR DTC 
    1. Turn the ignition switch to ON.
    2. Clear the DTCs.Refer to DTC CHECK / CLEAR .

      HINT: 

      First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.

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

      OK

      DTC B1790 is not output.

      HINT: 

      DTCs other than DTC B1790 may be output at this time, but they are not related to this check.

    NG → REPLACE CENTER AIRBAG SENSOR ASSEMBLY 

    OK → END 

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