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Home >> Infiniti >> 2024 >> QX55 Essential >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Can System (DTC/Circuit Diagnosis) >> Circuit Diagnosis >> It Can Communication Circuit >> Diagnosis Procedure

Diagnosis Procedure

  1. CHECK CAN DIAGNOSIS 

    Check the CAN diagnosis results from CONSULT to see that the vehicle CAN communication 2 circuit has no malfunction.

    Is the vehicle CAN communication 2 circuit normal?

    >>

    GO TO 2.

    >>

    Check and repair vehicle CAN communication 2 circuit.

  2. CONNECTOR INSPECTION 
    1. Turn the ignition switch OFF.
    2. Disconnect the battery cable from the negative terminal.
    3. Check the terminals and connectors of the 3CH CAN gateway for damage, bend and loose connection (unit side and connector side).

    Is the inspection result normal?

    >>

    GO TO 3.

    >>

    Repair the terminal and connector.

  3. CHECK HARNESS CONTINUITY (OPEN CIRCUIT) 
    1. Disconnect the connector of 3CH CAN gateway.
    2. Check the continuity between the 3CH CAN gateway harness connector terminals.
      3CH CAN gateway harness connector Continuity
      Connector No. Terminal No.
      M454 9 13 Existed
      10 14 Existed

    Is the inspection result normal?

    >>

    GO TO 4.

    >>

    Check the harness and repair or replace the root cause.

  4. CHECK HARNESS CONTINUITY (SHORT CIRCUIT) 
    1. Disconnect all the unit connectors on IT CAN communication circuit.
    2. Check the continuity between the 3CH CAN gateway harness connector terminals.
      3CH CAN gateway harness connector Continuity
      Connector No. Terminal No.
      M454 9 10 Not existed

    Is the inspection result normal?

    >>

    GO TO 5.

    >>

    Check the harness and repair or replace the root cause.

  5. CHECK HARNESS CONTINUITY (SHORT CIRCUIT) 

    Check the continuity between the 3CH CAN gateway harness connector and the ground.

    3CH CAN gateway harness connector Ground Continuity
    Connector No. Terminal No.
    M454 9 Not existed
    10 Not existed

    Is the inspection result normal?

    >>

    GO TO 6.

    >>

    Check the harness and repair or replace the root cause.

  6. CHECK 3CH CAN GATEWAY TERMINATION CIRCUIT 
    1. Remove the 3CH CAN gateway.
    2. Check the resistance between the 3CH CAN gateway terminals.
      3CH CAN gateway Resistance (Ω)
      Terminal No.
      9 10 Approx. 108 - 132
      13 14 Approx. 108 - 132

    Is the measurement value within the specification?

    >>

    GO TO 7.

    >>

    Replace the 3CH CAN gateway.

  7. CHECK SYMPTOM 

    Connect all the connectors. Check if the symptoms described in the "Symptom (Results from interview with customer)" are reproduced.

    Inspection result

    Reproduced>>

    GO TO 8.

    >>

    Start the diagnosis again. Follow the trouble diagnosis procedure when past error is detected.

  8. CHECK UNIT REPRODUCTION 

    Perform the reproduction test as per the following procedure for each unit.

    1. Turn the ignition switch OFF.
    2. Disconnect the battery cable from the negative terminal.
    3. Disconnect one of the unit connectors of IT CAN communication circuit.
      NOTE: SYMBOL 3CH CAN gateway has two termination circuits. Check other units first.
    4. Connect the battery cable to the negative terminal. Check if the symptoms described in the "Symptom (Results from interview with customer)" are reproduced.
      NOTE: SYMBOL Although unit-related error symptoms occur, do not confuse them with other symptoms.

    Inspection result

    Reproduced>>

    Connect the connector. Check other units as per the above procedure.

    >>

    Replace the unit whose connector was disconnected.

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