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Nissan Sentra B18 (2020-2025) Service Manual: Trouble Diagnosis - Specification Value

Diagnosis Description

Diagnosis Description

ECM input/output valve when the engine control system operates normally.

Note:

The SP value is indicated when “DISPLAY TYPE” is “Line Graph”.

When the indicated value of “DATA MONITOR” mode is within the SP value, the engine control system is confirmed OK. When the indicated value of “DATA MONITOR” mode is not within the SP value, the engine control system may have one or more malfunctions.

The SP value is used to detect malfunctions that may affect the Engine Control System, but will not light the MIL.

The SP value will be displayed for the following three items:

  • B/FUEL SCHDL (The fuel injection pulse width programmed into ECM prior to any learned on board correction)

  • A/F ALPHA-B1 (The mean value of air-fuel ratio feedback correction factor per cycle)

  • MASS AIR FLOW SENSOR (Hz) (The signal frequency of the mass air flow sensor)

Component Function Check

Component Function Check

  1. START

    Make sure that all of the following conditions are satisfied.

    • Nissan Sentra Vehicle driven distance: More than 5,000 km (3,107 miles)

    • Atmospheric pressure: 98.3 - 104.3 kPa (1.003 - 1.064 kg/cm2, 14.25 - 15.12 psi)

    • Atmospheric temperature: 20 - 30°C (68 - 86°F)

    • Engine coolant temperature: 75 - 95°C (167 - 203°F)

    • Transmission: Warmed-up

      • After the engine is warmed up to normal operating temperature, drive Nissan Sentra vehicle until “ATF TEMP SEN” (CVT fluid temperature sensor signal) indicates more than 60°C (140°F).

    • Electrical load: Not applied*

    • Engine speed: Idle

    *: Rear window defogger switch, air conditioner switch, lighting switch are OFF. Steering wheel is straight ahead.

    >>

    GO TO 2.

  2. CHECK REFERENCE OF DATA MONITOR MODE

    With CONSULT

    Note:

    Perform “Reference” in “DATA MONITOR” mode in maximum scale display.

    1. Refer to Work Procedure.

    2. On CONSULT screen, select “ENGINE”>>“Data Monitor”.

    3. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    4. Select “B/FUEL SCHDL”, “A/F ALPHA-B1” and “MASS AIR FLOW SENSOR (Hz)”.

    5. Make sure that monitor items are within the SP value.

    Is the inspection result normal?

    YES >>

    END

    NO >>

    Refer to Diagnosis Procedure.

Diagnosis Procedure

Diagnosis Procedure

OVERALL SEQUENCE

DETAILED PROCEDURE

  1. CHECK “A/F ALPHA-B1”

    With CONSULT

    1. Start engine.

    2. Confirm that the testing conditions are met.Refer to Component Function Check.

    3. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    4. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    5. Select “A/F ALPHA-B1”.

      Note:

      Check “A/F ALPHA-B1” 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-1 >>

    Less than the SP value: GO TO 2.

    NO-2 >>

    More than the SP value: GO TO 3.

  2. CHECK “B/FUEL SCHDL”

    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”

    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-1 >>

    More than the SP value: GO TO 6.

    NO-2 >>

    Less than the SP value: GO TO 25.

  4. CHECK “A/F ALPHA-B1”

    1. Stop the engine.

    2. Disconnect PCV hose, and then plug it.

    3. Start engine.

    4. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    5. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    6. Select “A/F ALPHA-B1”.

    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.

      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 condition.

    >>

    INSPECTION END

  6. CHECK FUEL PRESSURE

    Check fuel pressure. (Refer to Work Procedure.)

    Is the inspection result normal?

    YES >>

    GO TO 9.

    NO-1 >>

    Fuel pressure is too high: Replace “fuel filter and fuel pump assembly”, Refer to Removal and Installation. and then GO TO 8.

    NO-2 >>

    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”, Refer to Removal and Installation. and then GO TO 8.

    NO >>

    Repair or replace and then GO TO 8.

  8. CHECK “A/F ALPHA-B1”

    1. Start engine.

    2. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    3. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    4. Select “A/F ALPHA-B1”.

    Is the measurement value within the SP value?

    YES >>

    INSPECTION END

    NO >>

    GO TO 9.

  9. PERFORM POWER BALANCE TEST

    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.

    1. Ignition coil and its circuit (Refer to Component Function Check.)

    2. Fuel injector and its circuit (Refer to Component Function Check.)

    3. Intake air leakage

    4. Low compression pressure (Refer to Inspection.)

    Is the inspection result normal?

    YES >>

    Replace fuel injector, Refer to Removal and Installation, and then GO TO 11.

    NO >>

    Repair or replace malfunctioning part and then GO TO 11.

  11. CHECK “A/F ALPHA-B1”

    1. Start engine.

    2. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    3. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    4. Select “A/F ALPHA-B1”.

    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.

    • For DTC P0130, Refer to DTC Description.

    • For DTC P0131, Refer to DTC Description.

    • For DTC P0132, Refer to DTC Description.

    • For DTC P014C, P014D, P015A, P015B, Refer to DTC Description.

    • For DTC P2096, P2097, Refer to DTC Description.

    Is any DTC detected?

    YES >>

    GO TO 15.

    NO >>

    GO TO 13.

  13. CHECK A/F SENSOR 1 CIRCUIT

    Perform DIAGNOSTIC PROCEDURE according to corresponding DTC.

    >>

    GO TO 14.

  14. CHECK “A/F ALPHA-B1”

    1. Start engine.

    2. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    3. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    4. Select “A/F ALPHA-B1”.

    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”

    1. Start engine.

    2. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    3. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    4. Select “A/F ALPHA-B1”.

    Is the measurement value within the SP value?

    YES >>

    INSPECTION END

    NO >>

    Detect malfunctioning part according to DTC Description.

  17. CHECK “B/FUEL SCHDL”

    1. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    2. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    3. Select “B/FUEL SCHDL”.

    Is the measurement value within the SP value?

    YES >>

    INSPECTION END

    NO-1 >>

    More than the SP value: GO TO 18.

    NO-2 >>

    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, generator, 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”, AND “B/FUEL SCHDL”

    1. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    2. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    3. Select “B/FUEL SCHDL” and “A/F ALPHA-B1”.

    Is the measurement value within the SP value?

    YES >>

    INSPECTION END

    NO >>

    “B/FUEL SCHDL” is more, “A/F ALPHA-B1” is 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”

    1. Start engine.

    2. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    3. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    4. Select “A/F ALPHA-B1”.

    Is the measurement value within the SP value?

    YES >>

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

    NO >>

    GO TO 23.

  23. CHECK “MASS AIR FLOW SENSOR (HZ)”

    1. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    2. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    3. Select “MASS AIR FLOW SENSOR (Hz)”.

    Is the measurement value within the SP value?

    YES >>

    GO TO 24.

    NO >>

    More than the SP value: Replace mass air flow sensor,Refer to Removal and Installation, and then GO TO 29.

  24. REPLACE ECM

    Replace ECM. Refer to Removal & Installation.

    >>

    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 of air cleaner element

    • Uneven dirt of air cleaner element

    • Improper specification of 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”

    1. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    2. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    3. Select “B/FUEL SCHDL”.

    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)”

    1. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    2. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    3. Select “MASS AIR FLOW SENSOR (Hz)”.

    Is the measurement value within the SP value?

    YES >>

    GO TO 28.

    NO >>

    Less than the SP value: Replace mass air flow sensor, Refer to Removal and Installation, 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 of PCV valve

    • Disconnection or cracks of EVAP purge hose, open stuck of EVAP canister purge volume control solenoid valve

    • Malfunctioning seal of rocker cover gasket

    • Disconnection, looseness, or cracks of hoses, such as vacuum hose, connecting to intake air system parts

    • Malfunctioning seal of intake air system, etc.

    >>

    GO TO 30.

  29. CHECK “A/F ALPHA-B1” AND “B/FUEL SCHDL”

    1. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    2. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    3. Select “B/FUEL SCHDL” and “A/F ALPHA-B1”.

    Is the measurement value within the SP value?

    YES >>

    INSPECTION END

    NO >>

    Detect malfunctioning part according to Symptom Table.

  30. CHECK “B/FUEL SCHDL”

    1. Select “DATA MONITOR” mode of “ENGINE” using CONSULT

    2. Select “Reference” and change “DISPLAY TYPE” to “Line Graph”.

    3. Select “B/FUEL SCHDL”.

    Is the measurement value within the SP value?

    YES >>

    INSPECTION END

    NO >>

    Detect malfunctioning part according to Symptom Table.

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