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Home >> Nissan-Datsun >> 2021 >> NV2500 HD S >> Repair and Diagnosis >> External Pages >> Different car >> Section 617 (Engine Control System (DTC/Circuit Diagnosis) (1 Of 17)) >> DTC/Circuit Diagnosis >> Trouble Diagnosis - Specification Value >> Diagnosis Procedure >> Detailed Procedure

Detailed Procedure

WARNING: This page is about a different car, the 2020 Infiniti QX60. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK "A/F ALPHA-B1" AND "A/F ALPHA-B2" 

    SYMBOL With CONSULT

    1. Start engine.
    2. Confirm that the testing conditions are met. Refer to Component Function Check .
    3. On CONSULT screen, select "ENGINE">>"Data Monitor".
    4. Select "Reference" and change "DISPLAY TYPE" to "Line Graph".
    5. Select "A/F ALPHA-B1" and "A/F ALPHA-B2".
    6. Make sure that each indication is within the SP value.
      NOTE: Check "A/F ALPHA-B1", "A/F ALPHA-B2" for approximately 1 minute because they may fluctuate. It is NG if the indication is out of the SP value even a little.

    Is the measurement value within the SP value?

    YES

    GO TO 17.

    NO

    Less than the SP value: GO TO 2 .

    NO

    More than the SP value: GO TO 3 .

  2. CHECK "B/FUEL SCHDL" 

    SYMBOL With CONSULT

    Select "B/FUEL SCHDL" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    GO TO 4.

    NO

    More than the SP value: GO TO 19 .

  3. CHECK "B/FUEL SCHDL" 

    SYMBOL With CONSULT

    Select "B/FUEL SCHDL" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    GO TO 6.

    NO

    More than the SP value: GO TO 6 .

    NO

    Less than the SP value: GO TO 25 .

  4. CHECK "A/F ALPHA-B1" AND "A/F ALPHA-B2" 

    SYMBOL With CONSULT

    1. Stop the engine.
    2. Disconnect PCV hose, and then plug it.
    3. Start engine.
    4. Select "A/F ALPHA-B1" and "A/F ALPHA-B2" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    GO TO 5.

    NO

    GO TO 6.

  5. CHANGE ENGINE OIL 
    1. Stop the engine.
    2. Change engine oil. Refer to Inspection .
      NOTE: This symptom may occur when a large amount of gasoline is mixed with engine oil because of driving conditions (such as when engine oil temperature does not rise enough since a journey distance is too short during winter). The symptom will not be detected after changing engine oil or changing driving conditions.

    INSPECTION END

  6. CHECK FUEL PRESSURE 

    Check fuel pressure. (Refer to Work Procedure .)

    Is the inspection result normal?

    YES

    GO TO 9.

    NO

    Fuel pressure is too high: Replace "fuel filter and fuel pump assembly" and then GO TO 8.

    NO

    Fuel pressure is too low: GO TO 7 .

  7. DETECT MALFUNCTIONING PART 

    Check fuel hoses and fuel tubes for clogging.

    Is the inspection result normal?

    YES

    Replace "fuel filter and fuel pump assembly" and then GO TO 8.

    NO

    Repair or replace and then GO TO 8.

  8. CHECK "A/F ALPHA-B1" AND "A/F ALPHA-B2" 

    SYMBOL With CONSULT

    1. Start engine.
    2. Select "A/F ALPHA-B1" and "A/F ALPHA-B2" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    INSPECTION END

    NO

    GO TO 9.

  9. PERFORM POWER BALANCE TEST 

    SYMBOL With CONSULT

    1. Perform "POWER BALANCE" in "Active Test" mode.
    2. Make sure that the each cylinder produces a momentary engine speed drop.

    Is the inspection result normal?

    YES

    GO TO 12.

    NO

    GO TO 10.

  10. DETECT MALFUNCTIONING PART 

    Check the following bellow.

    Is the inspection result normal?

    YES

    Replace fuel injector and then GO TO 11.

    NO

    Repair or replace malfunctioning part and then GO TO 11.

  11. CHECK "A/F ALPHA-B1" AND "A/F ALPHA-B2" 

    SYMBOL With CONSULT

    1. Start engine.
    2. Select "A/F ALPHA-B1" and "A/F ALPHA-B2" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    INSPECTION END

    NO

    GO TO 12.

  12. CHECK A/F SENSOR 1 FUNCTION 

    Perform all DTC CONFIRMATION PROCEDURE related with A/F sensor 1.

    Are any DTCs detected?

    YES

    GO TO 13.

    NO

    GO TO 15.

  13. CHECK A/F SENSOR 1 CIRCUIT 

    Perform Diagnosis Procedure according to corresponding DTC.

    GO TO 14.

  14. CHECK "A/F ALPHA-B1" AND "A/F ALPHA-B2" 

    SYMBOL With CONSULT

    1. Start engine.
    2. Select "A/F ALPHA-B1" and "A/F ALPHA-B2" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    INSPECTION END

    NO

    GO TO 15.

  15. DISCONNECT AND RECONNECT ECM HARNESS CONNECTOR 
    1. Stop the engine.
    2. Disconnect ECM harness connector. Check pin terminal and connector for damage, and then reconnect it.

    GO TO 16.

  16. CHECK "A/F ALPHA-B1" AND "A/F ALPHA-B2" 

    SYMBOL With CONSULT

    1. Start engine.
    2. Select "A/F ALPHA-B1" and "A/F ALPHA-B2" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    INSPECTION END

    NO

    Detect malfunctioning part according to Symptom Table .

  17. CHECK "B/FUEL SCHDL" 

    SYMBOL With CONSULT

    Select "B/FUEL SCHDL" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    INSPECTION END

    NO

    More than the SP value: Go To 18 .

    NO

    Less than the SP value: Go to 25 .

  18. DETECT MALFUNCTIONING PART 
    1. Check for the cause of large engine friction. Refer to the following.
      • Engine oil level is too high
      • Engine oil viscosity
      • Belt tension of power steering, alternator, A/C compressor, etc. is excessive
      • Noise from engine
      • Noise from transmission, etc.
    2. Check for the cause of insufficient combustion. Refer to the following.
      • Valve clearance malfunction
      • Intake valve timing control function malfunction
      • Camshaft sprocket installation malfunction, etc.

    Repair or replace malfunctioning part, and then GO TO 30.

  19. CHECK INTAKE SYSTEM 

    Check for the cause of uneven air flow through mass air flow sensor. Refer to the following.

    • Crushed air ducts
    • Malfunctioning seal of air cleaner element
    • Uneven dirt of air cleaner element
    • Improper specification of intake air system

    Is the inspection result normal?

    YES

    GO TO 21.

    NO

    Repair or replace malfunctioning part, and then GO TO 20.

  20. CHECK "A/F ALPHA-B1", "A/F ALPHA-B2", AND "B/FUEL SCHDL" 

    SYMBOL With CONSULT

    Select "A/F ALPHA-B1", "A/F ALPHA-B2", and "B/FUEL SCHDL" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    INSPECTION END

    NO

    "B/FUEL SCHDL" is more, "A/F ALPHA-B1", "A/F ALPHA-B2" are less than the SP value: GO TO 21.

  21. DISCONNECT AND RECONNECT MASS AIR FLOW SENSOR HARNESS CONNECTOR 
    1. Stop the engine.
    2. Disconnect mass air flow sensor harness connector. Check pin terminal and connector for damage and then reconnect it again.

    GO TO 22.

  22. CHECK "A/F ALPHA-B1" AND "A/F ALPHA-B2" 

    SYMBOL With CONSULT

    1. Start engine.
    2. Select "A/F ALPHA-B1" and "A/F ALPHA-B2" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    Detect malfunctioning part of mass air flow sensor circuit and repair it. Refer to Diagnosis Procedure . Then GO TO 29.

    NO

    GO TO 23.

  23. CHECK "MASS AIR FLOW SENSOR (Hz)" 

    SYMBOL With CONSULT

    Select "MASS AIR FLOW SENSOR (Hz)" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    GO TO 24.

    NO

    More than the SP value: Replace malfunctioning mass air flow sensor, and then GO TO 29.

  24. REPLACE ECM 
    1. Replace ECM. Refer to Removal and Installation .
    2. Proceed to Description .

    GO TO 29.

  25. CHECK INTAKE SYSTEM 

    Check for the cause of uneven air flow through mass air flow sensor. Refer to the following.

    • Crushed air ducts
    • Malfunctioning seal in air cleaner element
    • Uneven dirt in air cleaner element
    • Improper specification in intake air system

    Is the inspection result normal?

    YES

    GO TO 27.

    NO

    Repair or replace malfunctioning part, and then GO TO 26.

  26. CHECK "B/FUEL SCHDL" 

    SYMBOL With CONSULT

    Select "B/FUEL SCHDL" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    INSPECTION END

    NO

    Less than the SP value: Go to 27 .

  27. CHECK "MASS AIR FLOW SENSOR (Hz)" 

    SYMBOL With CONSULT

    Select "MASS AIR FLOW SENSOR (Hz)" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    GO TO 28.

    NO

    Less than the SP value: Replace malfunctioning mass air flow sensor, and then GO TO 30.

  28. CHECK INTAKE SYSTEM 

    Check for the cause of air leak after the mass air flow sensor. Refer to the following.

    • Disconnection, looseness, and cracks in air duct
    • Looseness of oil filler cap
    • Disconnection of oil level gauge
    • Open stuck, breakage, hose disconnection, or cracks in PCV valve
    • Disconnection or cracks in EVAP purge hose, stuck open EVAP canister purge volume control solenoid valve
    • Malfunctioning seal in rocker cover gasket
    • Disconnection, looseness, or cracks in hoses, such as a vacuum hose, connecting to intake air system parts
    • Malfunctioning seal in intake air system, etc.

    GO TO 30.

  29. CHECK "A/F ALPHA-B1", "A/F ALPHA-B2", AND "B/FUEL SCHDL" 

    SYMBOL With CONSULT

    Select "A/F ALPHA-B1", "A/F ALPHA-B2", and "B/FUEL SCHDL" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    INSPECTION END

    NO

    Detect malfunctioning part according to Symptom Table .

  30. CHECK "B/FUEL SCHDL" 

    SYMBOL With CONSULT

    Select "B/FUEL SCHDL" at "Reference" of "Data Monitor" mode, and make sure that the indication is within the SP value.

    Is the measurement value within the SP value?

    YES

    INSPECTION END

    NO

    Detect malfunctioning part according to Symptom Table .

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