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Home >> Lexus >> 2017 >> GS 200t Base >> Repair and Diagnosis (Single Page) >> Restraints >> Air Bag, SRS >> Occupant Classification System - Diagnostic Codes & Symptom Tests >> Occupant Classification System >> DTC B1790: Center Airbag Sensor Assembly Communication Circuit Malfunction [09/2014 - ] >> Procedure

DTC B1790: Center Airbag Sensor Assembly Communication Circuit Malfunction [09/2014 - ]: Procedure

  1. CHECK FOR DTC 
    1. Turn the engine switch on (IG), and wait for at least 60 seconds.
    2. Clear the DTCs (Refer to DTC CHECK / CLEAR [09/2014 - ] ).

      HINT: 

      • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the center airbag sensor.
      • Use the Techstream to clear the DTCs of the occupant detection 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. Check for DTCs (Refer to DTC CHECK / CLEAR [09/2014 - ] ).

      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 [09/2014 - ] )

    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 detection ECU and center airbag sensor.

      OK

      Connectors are properly connected.

    Result: 

    NG 

    CONNECT CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK CONNECTOR 
    1. Disconnect the connectors from the center airbag sensor and occupant detection ECU.
      GTY414866Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Check that the connectors (on the center airbag sensor side and occupant detection ECU side) are not damaged (Refer to DIAGNOSIS SYSTEM [09/2014 - ] ).

      OK

      Connectors are not deformed or damaged.

      TEXT IN ILLUSTRATION

      *1 Occupant Detection ECU
      *2 Center Airbag Sensor Assembly

    Result: 

    NG 

    REPLACE HARNESS AND CONNECTOR 

    Result: 

    OK 

    See step  4

  4. CHECK CENTER AIRBAG SENSOR CIRCUIT 
    1. Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
      GTY678494Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    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
      z12-7 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      z12-4 (FSR-) - Body ground
    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 9 (FSR+) and 17 (FSR-) of connector B.
      NOTE:

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

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      z12-7 (FSR+) - z12-4 (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
      z12-7 (FSR+) - z12-4 (FSR-) Always 1 MΩ or higher
      z12-7 (FSR+) - Body ground
      z12-4 (FSR-) - Body ground
      TEXT IN ILLUSTRATION

      *1 Occupant Detection ECU
      *2 Center Airbag Sensor Assembly
      *3 Connector E
      *4 Connector B
      *5 Service Wire
      *a Front view of wire harness connector
      (to Occupant Detection ECU)
      *b Rear view of wire harness connector
      (to Center Airbag Sensor Assembly)

    Result: 

    NG 

    See step  10

    Result: 

    OK 

    See step  5

  5. CHECK FOR DTC 
    1. Connect the connectors to the occupant detection ECU and 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 the DTCs (Refer to DTC CHECK / CLEAR [09/2014 - ] ).

      HINT: 

      • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the center airbag sensor.
      • Use the Techstream to clear the DTCs of the occupant detection 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. Check for DTCs (Refer to DTC CHECK / CLEAR [09/2014 - ] ).

      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 [09/2014 - ] )

    Result: 

    NG 

    See step  6

  6. CHECK OCCUPANT DETECTION 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 detection ECU (Refer to REMOVAL [09/2014 - ] ).

      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. Turn the engine switch on (IG).
    3. Perform the zero point calibration (Refer to INITIALIZATION [09/2014 - ] ).

      OK

      "Zero Point Calibration is complete." is displayed.

    Result: 

    NEXT 

    See step  8

  8. PERFORM SENSITIVITY CHECK 
    1. Perform the sensitivity check (Refer to INITIALIZATION [09/2014 - ] ).

      Standard

      27 to 33 kg (59.5 to 72.8 lb)

    Result: 

    NEXT 

    See step  9

  9. CHECK FOR DTC 
    1. Clear the DTCs (Refer to DTC CHECK / CLEAR [09/2014 - ] ).

      HINT: 

      • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the center airbag sensor.
      • Use the Techstream to clear the DTCs of the occupant detection 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. Check for DTCs (Refer to DTC CHECK / CLEAR [09/2014 - ] ).

      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 (OCCUPANT DETECTION ECU WAS DEFECTIVE) 

    Result: 

    NG 

    REPLACE CENTER AIRBAG SENSOR ASSEMBLY 

    (Refer to REMOVAL [09/2014 - ] )

  10. CHECK FRONT SEAT INNER BELT ASSEMBLY RH 
    1. Disconnect the front seat inner belt assembly RH connector from the floor wire.
      GTY527834Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    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
      T4-1 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      T4-4 (FSR-) - Body ground
    5. Turn the engine switch off.
    6. Disconnect the connector from the occupant detection ECU.
    7. Using a service wire, connect terminals 7 (FSR+) and 4 (FSR-) of connector E.
      NOTE:

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

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      T4-1 (FSR+) - T4-4 (FSR-) Always Below 1 Ω
    9. Disconnect the service wire from connector E.
    10. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      T4-1 (FSR+) - T4-4 (FSR-) Always 1 MΩ or higher
      T4-1 (FSR+) - Body ground
      T4-4 (FSR-) - Body ground
      TEXT IN ILLUSTRATION

      *1 Front Seat Inner Belt Assembly RH
      *2 Floor Wire
      *3 Occupant Detection ECU
      *4 Center Airbag Sensor Assembly
      *5 Service Wire
      *6 Connector E
      *7 Connector D
      *a Front view of wire harness connector
      (to Occupant Detection ECU)
      *b Front view of wire harness connector
      (to Floor Wire)

    Result: 

    OK 

    REPLACE FLOOR WIRE 

    Result: 

    NG 

    REPLACE FRONT SEAT INNER BELT ASSEMBLY RH 

    (Refer to REMOVAL [09/2014 - ] )

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