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Home >> Infiniti >> 2008 >> QX56 RWD >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Engine Control System - Introduction >> Component Diagnosis >> Power Supply And Ground Circuit >> Diagnosis Procedure
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Diagnosis Procedure

  1. INSPECTION START

    Start engine.

    Is engine running? 

    Yes or No 

    Yes: GO TO  8.

    No: GO TO 2.

  2. CHECK ECM POWER SUPPLY CIRCUIT-I
    1. Turn ignition switch OFF and then ON.
    2. Check voltage between ECM terminal 109 and ground with CONSULT-III or tester.

      Voltage: Battery voltage 

    OK or NG 

    OK: GO TO  4.

    NG: GO TO 3.

    Fig 1: Checking Voltage Between ECM Terminal 109 And Ground
    G05739317Courtesy of NISSAN MOTOR CO., U.S.A.
  3. DETECT MALFUNCTIONING PART

    Check the following.

    • 10A fuse
    • Harness for open or short between ECM and fuse

    Repair harness or connectors.

  4. CHECK GROUND CONNECTIONS
    1. Turn ignition switch OFF.
    2. Loosen and retighten three ground screws on the body.

      Refer to "GROUND INSPECTION ".

      Fig 2: Identifying Body Ground Screw
      G05739318Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO 5.

    NG: Repair or replace ground connections.

  5. CHECK ECM GROUND CIRCUIT FOR OPEN AND SHORT-I
    1. Disconnect ECM harness connector.
    2. Check harness continuity between ECM terminals 1, 115, 116 and ground.

      Refer to WIRING DIAGRAM .

      Continuity should exist. 

    3. Also check harness for short to power.

    OK or NG 

    OK: GO TO  7.

    NG: GO TO 6.

  6. DETECT MALFUNCTIONING PART

    Check the following.

    • Harness connectors F32, E2
    • Harness for open or short between ECM and ground

    Repair open circuit or short to power in harness or connectors.

  7. CHECK ECM POWER SUPPLY CIRCUIT-II
    1. Reconnect ECM harness connector.
    2. Turn ignition switch ON.
    3. Check voltage between IPDM E/R terminal 4 and ground with CONSULT-III or tester.

      Voltage: Battery voltage 

      Fig 3: Checking Voltage Between IPDM E/R Terminal 4 And Ground
      G05739319Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: Go to "DIAGNOSIS PROCEDURE ".

    NG: GO TO 8.

  8. CHECK ECM POWER SUPPLY CIRCUIT-III
    1. Turn ignition switch OFF and wait at least 10 seconds.
    2. Turn ignition switch ON and then OFF.
    3. Check voltage between ECM terminals 119, 120 and ground with CONSULT-III or tester.

      Voltage: After turning ignition switch OFF, battery voltage will exist for a few seconds, then drop approximately 0V. 

      Fig 4: Checking Voltage Between ECM Terminals
      G05739320Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO  13.

    NG (Battery voltage does not exist.): GO TO 9.

    NG (Battery voltage exists for more than a few seconds.): GO TO  11.

  9. CHECK ECM POWER SUPPLY CIRCUIT-IV
    1. Turn ignition switch OFF and wait at least 10 seconds.
    2. Check voltage between ECM terminal 111 and ground with CONSULT-III or tester.

      Voltage: Battery voltage 

      Fig 5: Checking Voltage Between ECM Terminal 111 And Ground
      G05739321Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO 10.

    NG: GO TO  11.

  10. CHECK ECM POWER SUPPLY CIRCUIT-V
    1. Disconnect ECM harness connector.
    2. Disconnect IPDM E/R harness connector E119.
    3. Check harness continuity between ECM terminals 119, 120 and IPDM E/R terminal 3.

      Refer to WIRING DIAGRAM .

      Continuity should exist. 

    4. Also check harness for short to ground and short to power.

    OK or NG 

    OK: GO TO  13.

    NG: Repair open circuit or short to ground or short to power in harness or connectors.

  11. CHECK ECM POWER SUPPLY CIRCUIT-VI
    1. Disconnect ECM harness connector.
    2. Disconnect IPDM E/R harness connector E119.
    3. Check harness continuity between ECM terminal 111 and IPDM E/R terminal 7.

      Refer to WIRING DIAGRAM .

      Continuity should exist. 

    4. Also check harness for short to ground and short to power.

    OK or NG 

    OK: GO TO 12.

    NG: Repair open circuit or short to ground or short to power in harness or connectors.

  12. CHECK 20A FUSE
    1. Disconnect 20A fuse from IPDM E/R.
    2. Check 20A fuse.

    OK or NG 

    OK: GO TO  16.

    NG: Replace 20A fuse.

  13. CHECK GROUND CONNECTIONS
    1. Turn ignition switch OFF.
    2. Loosen and retighten ground three screws on the body.

      Refer to "GROUND INSPECTION ".

      Fig 6: Identifying Body Ground Screw
      G05739322Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO 14.

    NG: Repair or replace ground connections.

  14. CHECK ECM GROUND CIRCUIT FOR OPEN AND SHORT-II
    1. Disconnect ECM harness connector.
    2. Check harness continuity between ECM terminals 1, 115, 116 and ground.

      Refer to WIRING DIAGRAM .

      Continuity should exist. 

    3. Also check harness for short to power.

    OK or NG 

    OK: GO TO  16.

    NG: GO TO 15.

  15. DETECT MALFUNCTIONING PART

    Check the following.

    • Harness connectors F32, E2
    • Harness for open or short between ECM and ground

    Repair open circuit or short to power in harness or connectors.

  16. CHECK INTERMITTENT INCIDENT

    Refer to "HOW TO CHECK TERMINAL " and "INTERMITTENT INCIDENT ".

    OK or NG 

    OK: Replace IPDM E/R.

    NG: Repair open circuit or short to power in harness or connectors.

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