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Home >> Lexus >> 2010 >> IS F >> Repair and Diagnosis (Single Page) >> Restraints >> Air Bag, SRS >> Occupant Classification System (Diagnostic Codes & Circuit Tests) >> 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 CONNECTORS 
    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 assembly. Also check that the connectors that link the front seat wire RH and floor wire are properly connected.

      OK

      The connectors are properly connected.

      HINT: 

      If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

    4. Disconnect the connectors from the center airbag sensor assembly and the occupant classification ECU. Also disconnect the connectors that link the front seat wire RH and floor wire.
    5. Check that the terminals of the connectors are not damaged.

      OK

      The terminals are not deformed or damaged.

    NG → REPLACE WIRE HARNESS 

    OK: Go to next step 

  2. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT TO B+) 
    1. Connect the connectors that link the front seat wire RH and floor wire.
      Fig 1: Checking Occupant Classification System Circuit For A Short
      GTY289455Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Connect the cable to the negative (-) battery terminal.
    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
      T16-11 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      T16-12 (FSR-) - Body ground Engine switch on (IG) Below 1 V

    NG → See step   12 

    OK: Go to next step 

  3. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (OPEN) 
    1. Turn the engine switch off.
      Fig 2: Checking Occupant Classification System Circuit An Open
      GTY121391Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    3. Using SST, connect terminals 12 (FSP+) and 13 (FSP-) of connector B.
      NOTE:

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

      • SST: 09843-18040 
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      T16-11 (FSR+) - T16-12 (FSR-) Always Below 1 Ω

    NG → See step   13 

    OK: Go to next step 

  4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT) 
    1. Disconnect SST from connector B.
      Fig 3: Checking Occupant Classification System Circuit For A Short
      GTY289455Courtesy 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
      T16-11 (FSR+) - T16-12 (FSR-) Always 1 MΩ or higher

    NG → See step   14 

    OK: Go to next step 

  5. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT TO GROUND) 
    1. Measure the resistance according to the value(s) in the table below.
      Fig 4: Checking Occupant Classification System Circuit For A Short
      GTY289455Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance

      Tester Connection Condition Specified Condition
      T16-11 (FSR+) - Body ground Always 1 MΩ or higher
      T16-12 (FSR-) - Body ground Always 1 MΩ or higher

    NG → See step   15 

    OK: Go to next step 

  6. RECHECK DTC 
    1. Connect the connectors to the occupant classification ECU and the center airbag sensor assembly.
    2. Connect the Techstream to the DLC3.
    3. Connect the cable to the negative (-) battery terminal.
    4. Turn the engine switch on (IG).
    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 assembly. Refer to DTC CHECK / CLEAR .
    7. Turn the engine switch off.
    8. Turn the engine switch on (IG).
    9. Using the Techstream, check for 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.

    NG → See step   7 

    OK → See step   16 

  7. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Using the Techstream, save the ECU data from the ECU currently installed on the vehicle. Refer to REGISTRATION .
    4. Turn the engine switch off.
    5. Disconnect the cable from the negative (-) battery terminal.
    6. Replace the occupant classification ECU. Refer to REMOVAL .
    7. Connect the cable to the negative (-) battery terminal.
    8. Turn the engine switch on (IG).
    9. Using the Techstream, load the previous ECU data stored into the new ECU. Refer to REGISTRATION .
    10. Turn the engine switch off.
    11. Turn the engine switch on (IG).
    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 

  8. RECHECK DTC 
    1. Turn the engine switch on (IG).
    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 engine switch off.
    5. Turn the engine switch on (IG).
    6. Using the Techstream, check for 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.

    NG → See step   10 

    OK: Go to next step 

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

    NEXT → END 

  10. REPLACE CENTER AIRBAG SENSOR ASSEMBLY 
    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 center airbag sensor assembly. Refer to REMOVAL .

    NEXT: Go to next step 

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

    NEXT → END 

  12. CHECK FLOOR WIRE (SHORT TO B+) 
    1. Turn the engine switch off.
      Fig 5: Checking Floor Wire For A Short
      GTY125988Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
    3. Disconnect the front seat wire RH connector from the floor wire.
    4. Connect the cable to the negative (-) battery terminal.
    5. Turn the engine switch on (IG).
    6. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      PT2-3 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      PT2-8 (FSR-) - Body ground Engine switch on (IG) Below 1 V

    NG → REPLACE FLOOR WIRE 

    OK → REPLACE FRONT SEAT WIRE RH 

  13. CHECK FLOOR WIRE (OPEN) 
    1. Disconnect the front seat wire RH connector from the floor wire.
      Fig 6: Checking Floor Wire For An Open
      GTY131769Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      HINT: 

      SST has already been inserted into connector B.

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      PT2-3 (FSR+) - PT2-8 (FSR-) Always Below 1 Ω

    NG → REPLACE FLOOR WIRE 

    OK → REPLACE FRONT SEAT WIRE RH 

  14. CHECK FLOOR WIRE (SHORT) 
    1. Disconnect the front seat wire RH connector from the floor wire.
      Fig 7: Checking Floor Wire For A Short
      GTY125988Courtesy 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
      PT2-3 (FSR+) - PT2-8 (FSR-) Always 1 MΩ or higher

    NG → REPLACE FLOOR WIRE 

    OK → REPLACE FRONT SEAT WIRE RH 

  15. CHECK FLOOR WIRE (SHORT TO GROUND) 
    1. Disconnect the front seat wire RH connector from the floor wire.
      Fig 8: Checking Floor Wire For A Short
      GTY125988Courtesy 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
      PT2-3 (FSR+) - Body ground Always 1 MΩ or higher
      PT2-8 (FSR-) - Body ground Always 1 MΩ or higher

    NG → REPLACE FLOOR WIRE 

    OK → REPLACE FRONT SEAT WIRE RH 

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