OCCUPANT CLASSIFICATION SYSTEM, Diagnostic DTC:B1790

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

DESCRIPTION

The center airbag sensor assembly communication circuit consists of the occupant classification ECU and center airbag sensor assembly.

DTC B1790 is recorded when a malfunction is detected in the center airbag sensor assembly communication circuit.

DTC No. DTC Detecting Condition Trouble Area
B1790

  • The occupant classification ECU receives a line short circuit signal, an open circuit signal, a short circuit to ground signal or a short circuit to B+ signal in the center airbag sensor assembly communication circuit.

  • Occupant classification ECU malfunction

  • Center airbag sensor assembly malfunction

  • Occupant classification ECU

  • Center airbag sensor assembly

  • Front seat wire RH

  • Floor wire No. 2

  • Junction connector

WIRING DIAGRAM

A01EJDPE01

INSPECTION PROCEDURE

Tech Tips


  • If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see the under surface of 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 a problem, such as seat rail deformation. Hold the seat only as necessary.

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 center airbag sensor assembly and occupant classification ECU. Also check that the connectors that link the front seat wire RH and No. 2 floor wire are properly connected.

      OK
      The connectors are properly connected.

      Tech Tips

      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 occupant classification ECU. Also disconnect the connectors that link the front seat wire RH and No. 2 floor wire.

    5. Check that the connector terminals are not damaged.

      OK
      The terminals are not deformed or damaged.

    NG

    REPLACE WIRE HARNESS

    OK

  2. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (OPEN)


    1. Turn the ignition switch off.

      A01EIQ7E01

    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

    3. Using SST, connect terminals 16 (FSR+) and 24 (FSR-) of connector B.

      Note

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

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      S12-8 (FSR+) - S12-4 (FSR-) Always Below 1 Ω
      Text in Illustration
      *1 Occupant Classification ECU *2 Center Airbag Sensor Assembly
      *3 Junction Connector *4

      Front view of wire harness connector

      (to Center Airbag Sensor Assembly)
      *5

      Front view of wire harness connector

      (to Occupant Classification ECU)

      		 *6 Connector B
      *7 Connector E - -

    NG

    CHECK NO. 2 FLOOR WIRE (OPEN) Click here

    OK

  3. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT)


    1. A01EJRUE02
      Text in Illustration
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor Assembly
      *3 Junction Connector
      *4

      Front view of wire harness connector

      (to Occupant Classification ECU)
      *5 Connector E

      Disconnect SST from connector B.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      S12-8 (FSR+) - S12-4 (FSR-) Always 1 MΩ or higher

    NG

    CHECK FRONT SEAT WIRE RH (OPEN) Click here

    OK

  4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT TO GROUND)


    1. A01EJRUE02
      Text in Illustration
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor Assembly
      *3 Junction Connector
      *4

      Front view of wire harness connector

      (to Occupant Classification ECU)
      *5 Connector E

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      S12-8 (FSR+) - Body ground Always 1 MΩ or higher
      S12-4 (FSR-) - Body ground Always 1 MΩ or higher

    NG

    CHECK NO. 2 FLOOR WIRE (SHORT) Click here

    OK

  5. RECHECK DTC


    1. Connect the connectors to the occupant classification ECU and center airbag sensor assembly.

    2. Connect the GTS 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 Click here.

    6. Clear the DTCs stored in the center airbag sensor assembly Click here.

    7. Turn the ignition switch off.

    8. Turn the ignition switch to ON.

    9. Using the GTS, check the DTCs of the occupant classification ECU Click here.

      OK
      DTC B1790 is not output.

      Tech Tips

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


    NG

    REPLACE OCCUPANT CLASSIFICATION ECU Click here

    OK

    USE SIMULATION METHOD TO CHECK Click here

  6. REPLACE OCCUPANT CLASSIFICATION ECU


    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 occupant classification ECU Click here.

      Tech Tips

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


    NEXT

  7. PERFORM ZERO POINT CALIBRATION


    1. Connect the cable to the negative (-) battery terminal.

    2. Connect the GTS to the DLC3.

    3. Turn the ignition switch to ON.

    4. Using the GTS, perform Zero Point Calibration Click here.

      OK
      "Zero Point Calibration is complete." is displayed.

    NEXT

  8. PERFORM SENSITIVITY CHECK


    1. Using the GTS, perform Sensitivity Check Click here.

      Standard
      27 to 33 kg (59.5 to 72.8 lb)

    NEXT

  9. RECHECK DTC


    1. Turn the ignition switch to ON.

    2. Clear the DTCs stored in the occupant classification ECU Click here.

    3. Clear the DTCs stored in the center airbag sensor assembly Click here.

    4. Turn the ignition switch off.

    5. Turn the ignition switch to ON.

    6. Using the GTS, check the DTCs of the occupant classification ECU Click here.

      OK
      DTC B1790 is not output.

      Tech Tips

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


    NG

    REPLACE CENTER AIRBAG SENSOR ASSEMBLY Click here

    OK

    END

  10. CHECK NO. 2 FLOOR WIRE (SHORT TO B+)


    1. A01EKPAE02
      Text in Illustration
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor Assembly
      *3 Front Seat Wire RH
      *4 Junction Connector
      *5 No. 2 Floor Wire
      *6

      Front view of wire harness connector

      (to Junction Connector)
      *7 Connector C

      Turn the ignition switch off.

    2. Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.

    3. Disconnect the junction 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
      M26-13 (FSR+) - Body ground Ignition switch ON Below 1 V
      M26-14 (FSR-) - Body ground Ignition switch ON Below 1 V

    NG

    REPLACE NO. 2 FLOOR WIRE

    OK

  11. CHECK FRONT SEAT WIRE RH (SHORT TO B+)


    1. A01EIYEE02
      Text in Illustration
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor Assembly
      *3 Front Seat Wire RH
      *4 Junction Connector
      *5 No. 2 Floor Wire
      *6

      Front view of wire harness connector

      (to Junction Connector)
      *7 Connector D

      Turn the ignition switch off.

    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 junction connector.

    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
      S14-14 (FSR+) - Body ground Ignition switch ON Below 1 V
      S14-13 (FSR-) - Body ground Ignition switch ON Below 1 V

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

    REPLACE JUNCTION CONNECTOR

  12. CHECK NO. 2 FLOOR WIRE (OPEN)


    1. Disconnect the junction connector from the No. 2 floor wire.

      A01ELFNE01

      Tech Tips

      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
      M26-13 (FSR+) - M26-14 (FSR-) Always Below 1 Ω
      Text in Illustration
      *1 Occupant Classification ECU *2 Center Airbag Sensor Assembly
      *3 Front Seat Wire RH *4 Junction Connector
      *5 No. 2 Floor Wire *6

      Front view of wire harness connector

      (to Center Airbag Sensor Assembly)
      *7

      Front view of wire harness connector

      (to Junction Connector)

      		 *8 Connector B
      *9 Connector C - -

    NG

    REPLACE NO. 2 FLOOR WIRE

    OK

  13. CHECK FRONT SEAT WIRE RH (OPEN)


    1. Disconnect the front seat wire RH connector from the junction connector.

      A01EMMNE02

    2. Using SST, connect terminals 8 (FSR+) and 4 (FSR-) of connector E.

      Note

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

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      S14-14 (FSR+) - S14-13 (FSR-) Always Below 1 Ω
      Text in Illustration
      *1 Occupant Classification ECU *2 Center Airbag Sensor Assembly
      *3 Front Seat Wire RH *4 Junction Connector
      *5 No. 2 Floor Wire *6

      Front view of wire harness connector

      (to Junction Connector)
      *7

      Front view of wire harness connector

      (to Occupant Classification ECU)

      		 *8 Connector D
      *9 Connector E - -

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

    REPLACE JUNCTION CONNECTOR

  14. CHECK NO. 2 FLOOR WIRE (SHORT)


    1. A01EKPAE02
      Text in Illustration
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor Assembly
      *3 Front Seat Wire RH
      *4 Junction Connector
      *5 No. 2 Floor Wire
      *6

      Front view of wire harness connector

      (to Junction Connector)
      *7 Connector C

      Disconnect the junction connector from the No. 2 floor wire.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      M26-13 (FSR+) - M26-14 (FSR-) Always 1 MΩ or higher

    NG

    REPLACE NO. 2 FLOOR WIRE

    OK

  15. CHECK FRONT SEAT WIRE RH (SHORT)


    1. A01EIYEE02
      Text in Illustration
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor Assembly
      *3 Front Seat Wire RH
      *4 Junction Connector
      *5 No. 2 Floor Wire
      *6

      Front view of wire harness connector

      (to Junction Connector)
      *7 Connector D

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

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      S14-14 (FSR+) - S14-13 (FSR-) Always 1 MΩ or higher

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

    REPLACE JUNCTION CONNECTOR

  16. CHECK NO. 2 FLOOR WIRE (SHORT TO GROUND)


    1. A01EKPAE02
      Text in Illustration
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor Assembly
      *3 Front Seat Wire RH
      *4 Junction Connector
      *5 No. 2 Floor Wire
      *6

      Front view of wire harness connector

      (to Junction Connector)
      *7 Connector C

      Disconnect the junction connector from the No. 2 floor wire.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      M26-13 (FSR+) - Body ground Always 1 MΩ or higher
      M26-14 (FSR-) - Body ground Always 1 MΩ or higher

    NG

    REPLACE NO. 2 FLOOR WIRE

    OK

  17. CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)


    1. A01EIYEE02
      Text in Illustration
      *1 Occupant Classification ECU
      *2 Center Airbag Sensor Assembly
      *3 Front Seat Wire RH
      *4 Junction Connector
      *5 No. 2 Floor Wire
      *6

      Front view of wire harness connector

      (to Junction Connector)
      *7 Connector D

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

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      S14-14 (FSR+) - Body ground Always 1 MΩ or higher
      S14-13 (FSR-) - Body ground Always 1 MΩ or higher

    NG

    REPLACE FRONT SEAT WIRE RH

    OK

    REPLACE JUNCTION CONNECTOR