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Home >> Lexus >> 2009 >> SC 430 >> Repair and Diagnosis (Single Page) >> Restraints >> Air Bag, SRS >> Occupant Classification System (Diagnostic Codes) >> Occupant Classification System >> DTC B1790: Center Airbag Sensor Assembly Communication Circuit Malfunction >> Procedure

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

  1. CHECK FOR DTC 
    1. Turn the ignition switch ON.
    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. Refer to REMOVAL .
    4. Turn the ignition switch OFF.
    5. Turn the ignition switch ON.
    6. Check for the DTCs. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1790 is not output.

      HINT: 

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

    OK → See step   11 

    NG: Go to next step 

  2. CHECK CONNECTION OF CONNECTOR 
    1. Turn the ignition switch OFF.
    2. Disconnect the negative (-) terminal cable from the battery.
    3. Check that the connectors are properly connected to the occupant classification ECU and the center airbag sensor.

      OK

      Connectors are properly connected.

    NG → CONNECT CONNECTORS PROPERLY 

    OK: Go to next step 

  3. CHECK CONNECTOR 
    1. Disconnect the connectors from the center airbag sensor and the occupant classification ECU.
    2. Check that the connectors (on the center airbag sensor side and occupant classification ECU side) are not damaged.

      OK

      Connectors are not deformed or damaged.

    NG → REPAIR OR REPLACE WIRE HARNESS 

    OK: Go to next step 

  4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT 
    1. Connect the negative (-) terminal cable to the battery.
      Fig 1: Occupant Classification Connector Terminals
      GTY137481Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Turn the ignition switch ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard voltage

      Tester Connection Switch Condition Specified Condition
      O3-11 (FSR+) - Body ground Ignition switch ON Below 1 V
      O3-12 (FSR-) - Body ground
    4. Turn the ignition switch OFF.
    5. Disconnect the negative (-) terminal cable from the battery.
    6. Using a service wire, connect terminals 16 (FSR+) and 24 (FSR-) of connector B.
      NOTE:

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

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

      Standard resistance

      Tester Connection Condition Specified Condition
      O3-11 (FSR+) - O3-12 (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
      O3-11 (FSR+) - O3-12 (FSR-) Always 1 MΩ or higher
      O3-11 (FSR+) - Body ground
      O3-12 (FSR-) - Body ground

    NG → See step   10 

    OK: Go to next step 

  5. CHECK FOR DTC 
    1. Connect the connectors to the occupant classification ECU and the center airbag sensor.
    2. Connect the Techstream to the DLC3.
    3. Connect the negative (-) terminal cable to the battery.
    4. Turn the ignition switch ON.
    5. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
    6. Clear the DTCs stored in the center airbag sensor. Refer to DTC CHECK / CLEAR .
    7. Turn the ignition switch OFF.
    8. Turn the ignition switch ON.
    9. Using the Techstream, check for the DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1790 is not output.

      HINT: 

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

    OK → See step   11 

    NG: Go to next step 

  6. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch ON.
    3. Using the Techstream, save the ECU data from the ECU which has been installed on the vehicle. Refer to REGISTRATION .
    4. Turn the ignition switch OFF.
    5. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    6. Replace the occupant classification ECU. Refer to DISASSEMBLY .
    7. Connect the negative (-) terminal cable to the battery.
    8. Turn the ignition switch ON.
    9. Using the Techstream, load the previous ECU data stored into the new ECU. Refer to REGISTRATION .
    10. Turn the ignition switch OFF.
    11. Turn the ignition switch ON.
    12. Clear the DTCs stored in the memory. Refer to DTC CHECK / CLEAR .

      HINT: 

      If the DTCs are not cleared at this time, past DTCs will remain.

    NEXT: Go to next step 

  7. CHECK FOR DTC 
    1. Turn the ignition switch ON.
    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. Refer to DTC CHECK / CLEAR .
    4. Turn the ignition switch OFF.
    5. Turn the ignition switch ON.
    6. Using the Techstream, check for the DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1790 is not output.

      HINT: 

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

    OK → See step   9 

    NG: Go to next step 

  8. REPLACE CENTER AIRBAG SENSOR ASSEMBLY 
    1. Turn the ignition switch OFF.
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Replace the center airbag sensor. Refer to REMOVAL .

    NEXT: Go to next step 

  9. PERFORM SENSITIVITY CHECK 
    1. Perform the sensitivity check. Refer to INITIALIZATION .

    NEXT → END 

  10. CHECK FLOOR WIRE 
    1. Turn the ignition switch OFF.
      Fig 2: Floor Wire Connector Terminals
      GTY134083Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Disconnect the front seat wire RH connector from the floor wire.
    4. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
    5. Turn the ignition switch ON.
    6. Measure the voltage according to the value(s) in the table below.

      Standard voltage

      Tester Connection Switch Condition Specified Condition
      BE2-6 (FSR+) - Body ground Ignition switch ON Below 1 V
      BE2-7 (FSR-) - Body ground
    7. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      BE2-6 (FSR+) - BE2-7 (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
      BE2-6 (FSR+) - BE2-7 (FSR-) Always 1 MΩ or higher
      BE2-6 (FSR+) - Body ground
      BE2-7 (FSR-) - Body ground

    NG → REPAIR OR REPLACE FLOOR WIRE 

    OK → REPAIR OR REPLACE FRONT SEAT WIRE RH 

  11. USE SIMULATION METHOD TO CHECK. Refer to  DIAGNOSIS SYSTEM 


  1. CHECK FOR DTC 
    1. Turn the ignition switch ON.
    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. Refer to REMOVAL .
    4. Turn the ignition switch OFF.
    5. Turn the ignition switch ON.
    6. Check for the DTCs. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1790 is not output.

      HINT: 

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

    OK → See step   11 

    NG: Go to next step 

  2. CHECK CONNECTION OF CONNECTOR 
    1. Turn the ignition switch OFF.
    2. Disconnect the negative (-) terminal cable from the battery.
    3. Check that the connectors are properly connected to the occupant classification ECU and the center airbag sensor.

      OK

      Connectors are properly connected.

    NG → CONNECT CONNECTORS PROPERLY 

    OK: Go to next step 

  3. CHECK CONNECTOR 
    1. Disconnect the connectors from the center airbag sensor and the occupant classification ECU.
    2. Check that the connectors (on the center airbag sensor side and occupant classification ECU side) are not damaged.

      OK

      Connectors are not deformed or damaged.

    NG → REPAIR OR REPLACE WIRE HARNESS 

    OK: Go to next step 

  4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT 
    1. Connect the negative (-) terminal cable to the battery.
      Fig 1: Occupant Classification Connector Terminals
      GTY137481Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Turn the ignition switch ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard voltage

      Tester Connection Switch Condition Specified Condition
      O3-11 (FSR+) - Body ground Ignition switch ON Below 1 V
      O3-12 (FSR-) - Body ground
    4. Turn the ignition switch OFF.
    5. Disconnect the negative (-) terminal cable from the battery.
    6. Using a service wire, connect terminals 16 (FSR+) and 24 (FSR-) of connector B.
      NOTE:

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

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

      Standard resistance

      Tester Connection Condition Specified Condition
      O3-11 (FSR+) - O3-12 (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
      O3-11 (FSR+) - O3-12 (FSR-) Always 1 MΩ or higher
      O3-11 (FSR+) - Body ground
      O3-12 (FSR-) - Body ground

    NG → See step   10 

    OK: Go to next step 

  5. CHECK FOR DTC 
    1. Connect the connectors to the occupant classification ECU and the center airbag sensor.
    2. Connect the Techstream to the DLC3.
    3. Connect the negative (-) terminal cable to the battery.
    4. Turn the ignition switch ON.
    5. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
    6. Clear the DTCs stored in the center airbag sensor. Refer to DTC CHECK / CLEAR .
    7. Turn the ignition switch OFF.
    8. Turn the ignition switch ON.
    9. Using the Techstream, check for the DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1790 is not output.

      HINT: 

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

    OK → See step   11 

    NG: Go to next step 

  6. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch ON.
    3. Using the Techstream, save the ECU data from the ECU which has been installed on the vehicle. Refer to REGISTRATION .
    4. Turn the ignition switch OFF.
    5. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    6. Replace the occupant classification ECU. Refer to DISASSEMBLY .
    7. Connect the negative (-) terminal cable to the battery.
    8. Turn the ignition switch ON.
    9. Using the Techstream, load the previous ECU data stored into the new ECU. Refer to REGISTRATION .
    10. Turn the ignition switch OFF.
    11. Turn the ignition switch ON.
    12. Clear the DTCs stored in the memory. Refer to DTC CHECK / CLEAR .

      HINT: 

      If the DTCs are not cleared at this time, past DTCs will remain.

    NEXT: Go to next step 

  7. CHECK FOR DTC 
    1. Turn the ignition switch ON.
    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. Refer to DTC CHECK / CLEAR .
    4. Turn the ignition switch OFF.
    5. Turn the ignition switch ON.
    6. Using the Techstream, check for the DTCs of the occupant classification ECU. Refer to DTC CHECK / CLEAR .

      OK

      DTC B1790 is not output.

      HINT: 

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

    OK → See step   9 

    NG: Go to next step 

  8. REPLACE CENTER AIRBAG SENSOR ASSEMBLY 
    1. Turn the ignition switch OFF.
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Replace the center airbag sensor. Refer to REMOVAL .

    NEXT: Go to next step 

  9. PERFORM SENSITIVITY CHECK 
    1. Perform the sensitivity check. Refer to INITIALIZATION .

    NEXT → END 

  10. CHECK FLOOR WIRE 
    1. Turn the ignition switch OFF.
      Fig 2: Floor Wire Connector Terminals
      GTY134083Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
    3. Disconnect the front seat wire RH connector from the floor wire.
    4. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
    5. Turn the ignition switch ON.
    6. Measure the voltage according to the value(s) in the table below.

      Standard voltage

      Tester Connection Switch Condition Specified Condition
      BE2-6 (FSR+) - Body ground Ignition switch ON Below 1 V
      BE2-7 (FSR-) - Body ground
    7. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      BE2-6 (FSR+) - BE2-7 (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
      BE2-6 (FSR+) - BE2-7 (FSR-) Always 1 MΩ or higher
      BE2-6 (FSR+) - Body ground
      BE2-7 (FSR-) - Body ground

    NG → REPAIR OR REPLACE FLOOR WIRE 

    OK → REPAIR OR REPLACE FRONT SEAT WIRE RH 

  11. USE SIMULATION METHOD TO CHECK. Refer to  DIAGNOSIS SYSTEM 
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