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Home >> Lexus >> 2009 >> ES 350 >> 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 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. Check 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   17 

    NG: Go to next step 

  2. CHECK CONNECTION OF CONNECTORS 
    1. Turn the engine 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 assembly.

      OK

      The connectors are properly connected.

    NG → CONNECT CONNECTORS PROPERLY, THEN GO TO STEP 1 

    OK: Go to next step 

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

      OK

      The connectors are not deformed or damaged.

    NG → REPAIR OR REPLACE WIRE HARNESS 

    OK: Go to next step 

  4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT TO B+) 
    1. Connect the negative (-) terminal cable to the battery.
      Fig 1: Identifying Occupant Classification System Circuit (Short To B+)
      GTY111505Courtesy 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 Condition Specified condition
      T4-11 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      T4-12 (FSR-) - Body ground Engine switch on (IG) Below 1 V

    NG → See step   13 

    OK: Go to next step 

  5. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (OPEN) 
    1. Turn the engine switch off.
      Fig 2: Identifying Occupant Classification System Circuit (Open)
      GTY121140Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the negative (-) terminal cable from the battery.
    3. with Rear side airbag:

      Using a service wire, connect terminals 16 (FSP+) and 24 (FSP-) of connector B.

      NOTE:

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

    4. without Rear side airbag:

      Using a service wire, connect terminals 12 (FSP+) and 13 (FSP-) of connector B.

      NOTE:

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

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

      Standard resistance

      Tester connection Condition Specified condition
      T4-11 (FSR+) - T4-12 (FSR-) Always Below 1 Ω

    NG → See step   14 

    OK: Go to next step 

  6. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT) 
    1. Disconnect the service wire from connector B.
      Fig 3: Identifying Occupant Classification System Circuit (For Short)
      GTY111505Courtesy 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
      T4-11 (FSR+) - T4-12 (FSR-) Always 1 MΩ or higher

    NG → See step   15 

    OK: Go to next step 

  7. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT TO GROUND) 
    1. Measure the resistance according to the value(s) in the table below.
      Fig 4: Identifying Occupant Classification System Circuit (For Short)
      GTY111505Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard resistance

      Tester connection Condition Specified condition
      T4-11 (FSR+) - Body ground Always 1 MΩ or higher
      T4-12 (FSR-) - Body ground Always 1 MΩ or higher

    NG → See step   16 

    OK: Go to next step 

  8. RECHECK DTC 
    1. Connect the connectors to the occupant classification ECU and the center airbag sensor assembly.
    2. Connect Techstream to the DLC3.
    3. Connect the negative (-) terminal cable to the battery.
    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 Techstream, check 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   17 

    NG: Go to next step 

  9. REPLACE OCCUPANT CLASSIFICATION ECU 
    1. Connect Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Using Techstream, save the ECU data from the ECU which has been installed on the vehicle . Refer to REGISTRATION .
    4. Turn the engine 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 REMOVAL .
    7. Connect the negative (-) terminal cable to the battery.
    8. Turn the engine switch on (IG).
    9. Using 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 

  10. 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 Techstream, check 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   12 

    NG: Go to next step 

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

    NEXT: Go to next step 

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

    NEXT → END 

  13. CHECK FLOOR WIRE NO. 2 (SHORT TO B+) 
    1. Turn the engine switch off.
      Fig 5: Checking Floor Wire No. 2 (For Short)
      GTY137604Courtesy 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 No. 2.
    4. Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.
    5. Turn the engine switch on (IG).
    6. Measure the voltage according to the value(s) in the table below.

      Standard voltage

      Tester connection Condition Specified condition
      MT2-1 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      MT2-4 (FSR-) - Body ground Engine switch on (IG) Below 1 V

    NG → REPAIR OR REPLACE FLOOR WIRE NO. 2 

    OK → REPAIR OR REPLACE FRONT SEAT WIRE RH 

  14. CHECK FLOOR WIRE NO. 2 (OPEN) 
    1. Disconnect the front seat wire RH connector from the floor wire No. 2.
      Fig 6: Identifying Floor Wire No. 2 (Open)
      GTY111506Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      HINT: 

      The service wire 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
      MT2-1 (FSR+) - MT2-4 (FSR-) Always Below 1 Ω

    NG → REPAIR OR REPLACE FLOOR WIRE NO. 2 

    OK → REPAIR OR REPLACE FRONT SEAT WIRE RH 

  15. CHECK FLOOR WIRE NO. 2 (SHORT) 
    1. Disconnect the front seat wire RH connector from the floor wire No. 2.
      Fig 7: Identifying Floor Wire No. 2 (Short)
      GTY137604Courtesy 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
      MT2-1 (FSR+) - MT2-4 (FSR-) Always 1 MΩ or higher

    NG → REPAIR OR REPLACE FLOOR WIRE NO. 2 

    OK → REPAIR OR REPLACE FRONT SEAT WIRE RH 

  16. CHECK FLOOR WIRE NO. 2 (SHORT TO GROUND) 
    1. Disconnect the front seat wire RH connector from the floor wire No. 2.
      Fig 8: Identifying Floor Wire No. 2 (Short To Ground)
      GTY137604Courtesy 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
      MT2-1 (FSR+) - Body ground Always 1 MΩ or higher
      MT2-4 (FSR-) - Body ground Always 1 MΩ or higher

    NG → REPAIR OR REPLACE FLOOR WIRE NO. 2 

    OK → REPAIR OR REPLACE FRONT SEAT WIRE RH 

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