OCCUPANT CLASSIFICATION SYSTEM, Diagnostic DTC:B1790

DTC Code DTC Name
B1790 Center Airbag Sensor Assembly Communication Circuit Malfunction

DESCRIPTION

The airbag ECU assembly communication circuit consists of the occupant detection ECU and airbag ECU assembly.

DTC B1790 is stored when a malfunction is detected in the airbag ECU assembly communication circuit.

DTC No. Detection Item DTC Detection Condition Trouble Area
B1790 Center Airbag Sensor Assembly Communication Circuit Malfunction

    One of the following conditions is met:

  • Occupant detection ECU detects a line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to +B signal in the airbag ECU assembly communication circuit for 2 seconds.

  • Airbag ECU assembly malfunction.

  • Occupant detection ECU malfunction.

  • Floor wire

  • Front seat wire RH

  • Occupant detection ECU

  • Airbag ECU assembly

Tech Tips


  • When DTC B1650/32 is stored as a result of troubleshooting the airbag system, perform troubleshooting for DTC B1790 of the occupant classification system.

  • Use the GTS to check for DTCs of the occupant detection ECU, otherwise the DTCs cannot be read.

WIRING DIAGRAM

B008IT0E24
*a Pf2
*b Occupant Detection ECU
*c Airbag ECU Assembly

CAUTION / NOTICE / HINT

Note


  • When disconnecting the cable, some systems need to be initialized after the cable is reconnected.

    Click here

  • After replacing the airbag ECU assembly, refer to initialization.

    Click here

Tech Tips


  • If troubleshooting (wire harness inspection) is difficult to perform, remove the front RH seat installation bolts to see the undersurface of the seat cushion.

  • In the above case, hold the seat so that it does not fall down. Holding the seat for a long period of time may cause problems, such as seat rail deformation. Hold the seat up only for as long as necessary.

PROCEDURE


  1. CHECK DTC


    1. Turn the engine switch on (IG), and wait for at least 60 seconds.

    2. Clear the DTCs.

      Click here


      Body Electrical > Occupant Detection > Clear DTCs

      Tech Tips


      • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the airbag ECU assembly.

      • Use the GTS 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.

      Click here


      Body Electrical > Occupant Detection > Trouble Codes
      Result
      Proceed to
      DTC B1790 is not output
      DTC B1790 is output

      Tech Tips

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


    DTC B1790 is not output

    USE SIMULATION METHOD TO CHECK Click here

    DTC B1790 is output

  2. CHECK CONNECTION OF 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 detection ECU and airbag ECU assembly.

      Result
      Proceed to
      Connectors are properly connected
      Connectors are not properly connected

    Connectors are not properly connected

    CONNECT CONNECTOR

    Connectors are properly connected

  3. CHECK CONNECTORS


    1. B008HEVC02
      *1 Occupant Detection ECU
      *2 Airbag ECU assembly
      *3 Front Seat Wire RH
      *4 Floor Wire

      Disconnect the connectors from the airbag ECU assembly and occupant detection ECU.

    2. Check that the connectors (on the airbag ECU assembly side and occupant detection ECU side) are not damaged.

      Result
      Proceed to
      Connectors are not deformed or damaged
      Connectors are deformed or damaged

    Connectors are deformed or damaged

    REPLACE FRONT SEAT WIRE RH OR FLOOR WIRE

    Connectors are not deformed or damaged

  4. CHECK AIRBAG ECU ASSEMBLY CIRCUIT


    1. B008JDEC07
      *1 Occupant Detection ECU
      *2 Airbag ECU 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 Airbag ECU Assembly)

      Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.

    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
      f15-7 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      f15-4 (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
      f15-7 (FSR+) - f15-4 (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
      f15-7 (FSR+) - f15-4 (FSR-) Always 1 MΩ or higher
      f15-7 (FSR+) - Body ground
      f15-4 (FSR-) - Body ground
      Result
      Proceed to
      OK
      NG

    NG

    CHECK FRONT SEAT WIRE RH Click here

    OK

  5. CHECK DTC


    1. Connect the connectors to the occupant detection ECU and airbag ECU assembly.

    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.

      Click here


      Body Electrical > Occupant Detection > Clear DTCs

      Tech Tips


      • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the airbag ECU assembly.

      • Use the GTS 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.

      Click here


      Body Electrical > Occupant Detection > Trouble Codes
      Result
      Proceed to
      DTC B1790 is not output
      DTC B1790 is output

      Tech Tips

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


    DTC B1790 is not output

    USE SIMULATION METHOD TO CHECK Click here

    DTC B1790 is output

  6. REPLACE 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.

      Click here

      Tech Tips

      Perform the inspection using parts from a normal vehicle when possible.

      Result
      Proceed to
      NEXT

    NEXT

  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.

      Click here

      Result
      Proceed to
      "Zero Point Calibration is complete." is displayed

    "Zero Point Calibration is complete." is displayed

  8. PERFORM SENSITIVITY CHECK


    1. Perform the sensitivity check.

      Click here

      Standard
      27 to 33 kg (59.5 to 72.8 lb)
      Result
      Proceed to
      NEXT

    NEXT

  9. CHECK DTC


    1. Clear the DTCs.

      Click here


      Body Electrical > Occupant Detection > Clear DTCs

      Tech Tips


      • First clear the DTCs stored in the occupant detection ECU, and then clear the DTCs stored in the airbag ECU assembly.

      • Use the GTS 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.

      Click here


      Body Electrical > Occupant Detection > Trouble Codes
      Result
      Proceed to
      DTC B1790 is not output
      DTC B1790 is output

      Tech Tips

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


    DTC B1790 is not output

    END (OCCUPANT DETECTION ECU WAS DEFECTIVE)

    DTC B1790 is output

    REPLACE AIRBAG ECU ASSEMBLY Click here

  10. CHECK FRONT SEAT WIRE RH


    1. B008J12C03
      *1 Front Seat Wire RH
      *2 Floor Wire
      *3 Occupant Detection ECU
      *4 Airbag ECU 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)

      Disconnect the front seat wire RH connector from the floor wire.

    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
      Pf2-7 (FSR+) - Body ground Engine switch on (IG) Below 1 V
      Pf2-3 (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 and 4 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
      Pf2-7 (FSR+) - Pf2-3 (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
      Pf2-7 (FSR+) - Pf2-3 (FSR-) Always 1 MΩ or higher
      Pf2-7 (FSR+) - Body ground
      Pf2-3 (FSR-) - Body ground
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE FLOOR WIRE

    NG

    REPLACE FRONT SEAT WIRE RH