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Home >> Infiniti >> 2012 >> M37 Base >> Repair and Diagnosis >> Steering >> Manual Steering >> Steering Control System (With 4WAS) >> DTC/Circuit Diagnosis >> DTC C1931: 4WAS Front Control Unit Communication >> Diagnosis Procedure
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Diagnosis Procedure

  1. CHECK COMMUNICATION LINE (1) 
    1. Turn the ignition switch OFF.
    2. Disconnect ABS actuator and electric unit (control unit) harness connector.
    3. Disconnect yaw rate/side/decel G sensor harness connector.
    4. Disconnect 4WAS front control unit harness connector.
    5. Disconnect 4WAS main control unit harness connector.
    6. Check the continuity between ABS actuator and electric unit (control unit) harness connector and yaw rate/side G sensor harness connector.
      ABS actuator and electric unit (control unit) Yaw rate/side/decel G sensor Continuity
      Connector Terminal Connector Terminal
      E41 6 M143 2 Existed
      16 3

      Is the inspection result normal? 

      YES: GO TO 2.

      NO: Repair or replace the harnesses and connectors. Refer to "PRECAUTIONS FOR HARNESS REPAIR ".

  2. CHECK COMMUNICATION LINE (2) 

    Check the continuity between ABS actuator and electric unit (control unit) harness connector and the ground.

    ABS actuator and electric unit (control unit) - Continuity
    Connector Terminal
    E41 6 Ground Not existed
    16

    Is the inspection result normal? 

    YES: GO TO 3.

    NO: Repair or replace the harnesses and connectors. Refer to "PRECAUTIONS FOR HARNESS REPAIR ".

  3. CHECK COMMUNICATION LINE (3) 

    Check the continuity between ABS actuator and electric unit (control unit) harness connector.

    ABS actuator and electric unit (control unit) Continuity
    Connector Terminal
    E41 6 16 Not existed

    Is the inspection result normal? 

    YES: GO TO 4.

    NO: Repair or replace the harnesses and connectors. Refer to "PRECAUTIONS FOR HARNESS REPAIR ".

  4. CHECK ABS ACTUATOR AND ELECTRIC UNIT (CONTROL UNIT) 

    Check the ABS actuator and electric unit (control unit) connector. Refer to "COMPONENT INSPECTION [ABS ACTUATOR AND ELECTRIC UNIT (CONTROL UNIT)] ".

    Is the inspection result normal? 

    YES: GO TO 5.

    NO: Replace ABS actuator and electric unit (control unit). Refer to "REMOVAL AND INSTALLATION ".

  5. CHECK YAW RATE/SIDE/DECEL G SENSOR 

    Check the between yaw rate/side/decel G sensor connector. Refer to "COMPONENT INSPECTION (YAW RATE/SIDE/DECEL G SENSOR) ".

    Is the inspection result normal? 

    YES: GO TO 6.

    NO: Replace yaw rate/side G sensor. Refer to "REMOVAL AND INSTALLATION ".

  6. CHECK CAN DIAGNOSIS SUPPORT MONITOR (4WAS FRONT CONTROL UNIT) 

    With CONSULT 

    1. Connect ABS actuator and electric unit (control unit) harness connector.
    2. Connect yaw rate/side/decel G sensor harness connector.
    3. Connect 4WAS front control unit harness connector.
    4. Connect 4WAS main control unit harness connector.
    5. Start the engine.
      CAUTION: Never drive the vehicle.
    6. Perform CAN diagnosis support monitor for "4WAS(FRONT)".
    7. Check error history between 4WAS front control unit and 4WAS main control unit. Refer to "CONSULT FUNCTION ".

      What is the indicated item? 

      All items are "OK": GO TO 7.

      "TRANSMIT DIAG" is except "OK": GO TO 7.

      "4WAS(MAIN)" is except "OK": GO TO  8.

  7. CHECK 4WAS FRONT CONTROL UNIT CIRCUIT 
    1. Turn the ignition switch OFF.
    2. Disconnect 4WAS front control unit harness connector.
    3. Disconnect ABS actuator and electric unit (control unit) harness connector.
    4. Check the continuity between 4WAS front control unit harness connector and ABS actuator and electric unit (control unit) harness connector.
      4WAS front control unit ABS actuator and electric unit (control unit) Continuity
      Connector Terminal Connector Terminal
      M42 14 E41 6 Existed
      25 16
    5. Check that 4WAS front control unit connector No. 14 terminal and No. 25 are connected properly and not deformed.

      Is the inspection result normal? 

      YES: Replace 4WAS front control unit. Refer to "REMOVAL AND INSTALLATION ".

      NO: Repair or replace the harnesses and connectors. Refer to "PRECAUTIONS FOR HARNESS REPAIR ".

  8. CHECK 4WAS MAIN CONTROL UNIT CIRCUIT 
    1. Turn the ignition switch OFF.
    2. Disconnect 4WAS main control unit harness connector.
    3. Disconnect ABS actuator and electric unit (control unit) harness connector.
    4. Check the continuity between 4WAS main control unit harness connector and ABS actuator and electric unit (control unit) harness connector.
      4WAS main control unit ABS actuator and electric unit (control unit) Continuity
      Connector Terminal Connector Terminal
      B54 31 E41 16 Existed
      32 6
    5. Check that 4WAS main control unit connector No. 31 terminal and No. 32 are connected properly and not deformed.

      Is the inspection result normal? 

      YES: Replace 4WAS main control unit. Refer to "REMOVAL AND INSTALLATION ".

      NO: Repair or replace the harnesses and connectors. Refer to "PRECAUTIONS FOR HARNESS REPAIR ".

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