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DTC B1790: Center Airbag Sensor Assembly Communication Circuit Malfunction [08/2019 - ]: Procedure

  1. CHECK FOR DTC 
    1. Turn the engine switch on (IG), and wait for at least 60 seconds.
    2. Clear any DTCs stored in the memory (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      HINT: 

      • First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.
      • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
    3. Turn the engine switch off.
    4. Turn the engine switch on (IG), and wait for at least 60 seconds.
    5. Using the Techstream, check for DTCs of the occupant classification ECU (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      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.

    Result: 

    OK 

    USE SIMULATION METHOD TO CHECK. Refer to  DIAGNOSIS SYSTEM [08/2019 - ] 

    Result: 

    NG 

    See step  2

  2. CHECK CONNECTION OF CONNECTOR 
    1. Turn the engine 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

      Connectors are properly connected.

    Result: 

    NG 

    CONNECT CONNECTORS PROPERLY 

    Result: 

    OK 

    See step  3

  3. CHECK CONNECTOR 
    1. Check that the connectors (on the center airbag sensor side and occupant classification ECU side) are not damaged (Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE [08/2019 - ] ).

      OK

      Connectors are not deformed or damaged.

      RESULT

      Result Proceed to
      Connectors are not deformed or damaged (for Power seat) A
      Connectors are not deformed or damaged (for Manual seat) B
      Connectors are deformed or damaged C

    Result: 

    B 

    See step  11

    Result: 

    C 

    REPLACE HARNESS OR CONNECTOR 

    Result: 

    A 

    See step  4

  4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT 
    1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
      GTY747127Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor
      *3 Front Seat Wire RH
      *4 No. 2 Floor Wire
      *5 Service Wire
      *a Front view of wire harness connector
      (to Occupant Classification ECU)
      *b Front view of wire harness connector
      (to Center Airbag Sensor)
    2. Turn the engine switch on (IG).
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      W6-8 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      W6-4 (FSR-) - Body ground Engine switch on (IG) Below 1 V
    4. Turn the engine switch off.
    5. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    6. Using a service wire, connect terminals 32 (FSR+) and 31 (FSR-) of connector B.
      NOTE:

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

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      W6-8 (FSR+) - W6-4 (FSR-) Always Below 1 Ω
    8. Disconnect the service wire from connector B.
    9. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      W6-8 (FSR+) - W6-4 (FSR-) Always 1 MΩ or higher
      W6-8 (FSR+) - Body ground Always 1 MΩ or higher
      W6-4 (FSR-) - Body ground Always 1 MΩ or higher

    Result: 

    NG 

    See step  10

    Result: 

    OK 

    See step  5

  5. 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 engine switch on (IG), and wait for at least 60 seconds.
    4. Clear any DTCs stored in the memory (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      HINT: 

      • First clear any DTCs stored in the occupant classification ECU and then in the center airbag sensor.
      • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
    5. Turn the engine switch off.
    6. Turn the engine switch on (IG), and wait for at least 60 seconds.
    7. Using the Techstream, check for DTCs of the occupant classification ECU (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      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.

    Result: 

    OK 

    USE SIMULATION METHOD TO CHECK. Refer to  DIAGNOSIS SYSTEM [08/2019 - ] 

    Result: 

    NG 

    See step  6

  6. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Turn the engine 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 REMOVAL [08/2019 - ] ).

      HINT: 

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

    Result: 

    NEXT 

    See step  7

  7. 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 engine switch on (IG), and wait for at least 60 seconds.
    4. Using the Techstream, perform the zero point calibration (Refer to INITIALIZATION [08/2019 - ] ).

    Result: 

    NEXT 

    See step  8

  8. PERFORM SENSITIVITY CHECK 
    1. Using the Techstream, perform the sensitivity check (Refer to INITIALIZATION [08/2019 - ] ).

      Standard range

      27 to 33 kg (59.5 to 72.8 lb)

    Result: 

    NEXT 

    See step  9

  9. CHECK FOR DTC 
    1. Clear any DTCs stored in the memory (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      HINT: 

      • First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.
      • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
    2. Turn the engine switch off.
    3. Turn the engine switch on (IG), and wait for at least 60 seconds.
    4. Using the Techstream, check for DTCs of the occupant classification ECU (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      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.

    Result: 

    OK 

    END 

    Result: 

    NG 

    REPLACE CENTER AIRBAG SENSOR. Refer to  REMOVAL [08/2019 - ] 

  10. CHECK NO. 2 FLOOR WIRE 
    1. Disconnect the front seat wire RH connector from the No. 2 floor wire.
      GTY752058Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor
      *3 Front Seat Wire RH
      *4 No. 2 Floor Wire
      *5 Service Wire
      *a Front view of wire harness connector
      (to Front Seat Wire RH)
      *b Front view of wire harness connector
      (to Center Airbag Sensor)
    2. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
    3. Turn the engine switch on (IG).
    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      PW1-8 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      PW1-9 (FSR-) - Body ground Engine switch on (IG) Below 1 V
    5. Turn the engine switch off.
    6. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    7. Using a service wire, connect terminals 32 (FSR+) and 31 (FSR-) of connector B.
      NOTE:

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

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      PW1-8 (FSR+) - PW1-9 (FSR-) Always Below 1 Ω
    9. Disconnect the service wire from connector B.
    10. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      PW1-8 (FSR+) - PW1-9 (FSR-) Always 1 MΩ or higher
      PW1-8 (FSR+) - Body ground Always 1 MΩ or higher
      PW1-9 (FSR-) - Body ground Always 1 MΩ or higher

    Result: 

    OK 

    REPLACE FRONT SEAT WIRE RH 

    Result: 

    NG 

    REPLACE NO. 2 FLOOR WIRE 

  11. CHECK NO. 2 FLOOR WIRE 
    1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
      GTY746753Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor
      *3 No. 2 Floor Wire
      *4 Service Wire
      *a Front view of wire harness connector
      (to Occupant Classification ECU)
      *b Front view of wire harness connector
      (to Center Airbag Sensor)
    2. Turn the engine switch on (IG).
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      P14-8 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      P14-4 (FSR-) - Body ground Engine switch on (IG) Below 1 V
    4. Turn the engine switch off.
    5. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    6. Using a service wire, connect terminals 32 (FSR+) and 31 (FSR-) of connector B.
      NOTE:

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

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      P14-8 (FSR+) - P14-4 (FSR-) Always Below 1 Ω
    8. Disconnect the service wire from connector B.
    9. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      P14-8 (FSR+) - P14-4 (FSR-) Always 1 MΩ or higher
      P14-8 (FSR+) - Body ground Always 1 MΩ or higher
      P14-4 (FSR-) - Body ground Always 1 MΩ or higher

    Result: 

    NG 

    REPLACE NO. 2 FLOOR WIRE 

    Result: 

    OK 

    See step  12

  12. 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 engine switch on (IG), and wait for at least 60 seconds.
    4. Clear any DTCs stored in the memory (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      HINT: 

      • First clear any DTCs stored in the occupant classification ECU and then in the center airbag sensor.
      • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
    5. Turn the engine switch off.
    6. Turn the engine switch on (IG), and wait for at least 60 seconds.
    7. Using the Techstream, check for DTCs of the occupant classification ECU (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      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.

    Result: 

    OK 

    USE SIMULATION METHOD TO CHECK. Refer to  DIAGNOSIS SYSTEM [08/2019 - ] 

    Result: 

    NG 

    See step  13

  13. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Turn the engine 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 REMOVAL [08/2019 - ] ).

      HINT: 

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

    Result: 

    NEXT 

    See step  14

  14. 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 engine switch on (IG), and wait for at least 60 seconds.
    4. Using the Techstream, perform the zero point calibration (Refer to INITIALIZATION [08/2019 - ] ).

    Result: 

    NEXT 

    See step  15

  15. PERFORM SENSITIVITY CHECK 
    1. Using the Techstream, perform the sensitivity check (Refer to INITIALIZATION [08/2019 - ] ).

      Standard range

      27 to 33 kg (59.5 to 72.8 lb)

    Result: 

    NEXT 

    See step  16

  16. CHECK FOR DTC 
    1. Clear any DTCs stored in the memory (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      HINT: 

      • First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.
      • Use the Techstream to clear the DTCs of the occupant classification ECU, otherwise the DTCs cannot be cleared.
    2. Turn the engine switch off.
    3. Turn the engine switch on (IG), and wait for at least 60 seconds.
    4. Using the Techstream, check for DTCs of the occupant classification ECU (Refer to DTC CHECK / CLEAR [08/2019 - ] ).

      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.

    Result: 

    OK 

    END 

    Result: 

    NG 

    REPLACE CENTER AIRBAG SENSOR. Refer to  REMOVAL [08/2019 - ] 

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