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

  1. CHECK CONNECTORS 
    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 assembly.

      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.
    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 cable to the negative (-) battery terminal.
      Fig 1: Checking Occupant Classification System Circuit
      GTY184150Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Turn the ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      R2-11 (FSR+) - Body ground Ignition switch ON Below 1 V
      R2-12 (FSR-) - Body ground Ignition switch ON Below 1 V

    NG → See step   12 

    OK: Go to next step 

  3. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (OPEN) 
    1. Turn the ignition switch off.
      Fig 2: Checking Occupant Classification System Circuit (Open)
      GTY179625Courtesy 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 (FSR+) and 13 (FSR-) 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
      R2-11 (FSR+) - R2-12 (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
      GTY184150Courtesy 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
      R2-11 (FSR+) - R2-12 (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
      GTY184150Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Resistance

      Tester Connection Condition Specified Condition
      R2-11 (FSR+) - Body ground Always 1 MΩ or higher
      R2-12 (FSR-) - Body ground Always 1 MΩ or higher

    NG → See step   15 

    OK: Go to next step 

  6. RECHECK FOR 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 ignition switch to 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 assembly. Refer to DTC CHECK / CLEAR .
    7. Turn the ignition switch off.
    8. Turn the ignition switch to ON.
    9. Using the Techstream, check for occupant classification ECU 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.

    NG → See step   7 

    OK → See step   16 

  7. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Using the Techstream, save the ECU data from the ECU currently installed on the vehicle. Refer to REGISTRATION .
    4. Turn the ignition 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 ignition switch to 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 to 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 

  8. RECHECK FOR DTC 
    1. Turn the ignition switch to 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 assembly. Refer to DTC CHECK / CLEAR .
    4. Turn the ignition switch off.
    5. Turn the ignition switch to ON.
    6. Using the Techstream, check for occupant classification ECU 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.

    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 ignition 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 NO. 2 FLOOR WIRE (SHORT TO B+) 
    1. Turn the ignition switch off.
      Fig 5: Checking No. 2 Floor Wire
      GTY172523Courtesy 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 No. 2 floor wire.
    4. Connect the cable to the negative (-) battery terminal.
    5. Turn the ignition switch to ON.
    6. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      MR1-5 (FSR+) - Body ground Ignition switch ON Below 1 V
      MR1-10 (FSR-) - Body ground Ignition switch ON Below 1 V

    NG → REPLACE NO. 2 FLOOR WIRE 

    OK → REPLACE FRONT SEAT WIRE RH 

  13. CHECK NO. 2 FLOOR WIRE (OPEN) 
    1. Disconnect the front seat wire RH connector from the No. 2 floor wire.
      Fig 6: Checking No. 2 Floor Wire (Open)
      GTY169019Courtesy 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
      MR1-5 (FSR+) - MR1-10 (FSR-) Always Below 1 Ω

    NG → REPLACE NO. 2 FLOOR WIRE 

    OK → REPLACE FRONT SEAT WIRE RH 

  14. CHECK NO. 2 FLOOR WIRE (SHORT) 
    1. Disconnect the front seat wire RH connector from the No. 2 floor wire.
      Fig 7: Checking No. 2 Floor Wire
      GTY172523Courtesy 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
      MR1-5 (FSR+) - MR1-10 (FSR-) Always 1 MΩ or higher

    NG → REPLACE NO. 2 FLOOR WIRE 

    OK → REPLACE FRONT SEAT WIRE RH 

  15. CHECK NO. 2 FLOOR WIRE (SHORT TO GROUND) 
    1. Disconnect the front seat wire RH connector from the No. 2 floor wire.
      Fig 8: Checking No. 2 Floor Wire
      GTY172523Courtesy 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
      MR1-5 (FSR+) - Body ground Always 1 MΩ or higher
      MR1-10 (FSR-) - Body ground Always 1 MΩ or higher

    NG → REPLACE NO. 2 FLOOR WIRE 

    OK → REPLACE FRONT SEAT WIRE RH 

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