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Home >> Infiniti >> 2017 >> QX80 Base, RWD >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System (DTCS) (2 Of 4) >> DTC/Circuit Diagnosis >> DTC P0172, P0175: Fuel Injection System Function >> Diagnosis Procedure >> Diagnostic Test
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Diagnostic Test

  1. CHECK EXHAUST GAS LEAKAGE

    1. Start engine and run it at idle.
    2. Listen for an exhaust gas leakage before three way catalyst (manifold).
      G04191081Courtesy of NISSAN NORTH AMERICA, INC.

    Is exhaust gas leakage detected?

    YES 

    Repair or replace malfunctioning part.

    NO 

    GO TO STEP 2  .

  2. CHECK FOR INTAKE AIR LEAKAGE

    Listen for an intake air leakage after the mass air flow sensor.

    Is intake air leakage detected?

    YES 

    Repair or replace malfunctioning part.

    NO 

    GO TO STEP 3  .

  3. CHECK A/F SENSOR 1 CIRCUIT

    1. Turn ignition switch OFF.
    2. Disconnect corresponding A/F sensor 1 harness connector.
    3. Disconnect ECM harness connector.
    4. Check the continuity between A/F sensor 1 harness connector and ECM harness connector.
      DTC A/F sensor 1 ECM Continuity
      Bank Connector Terminal Connector Terminal
      P0172 1 F89 1 F92 79 Existed
      2 74
      P0175 2 F90 1 F92 69
      2 70
    5. Check the continuity between A/F sensor 1 harness connector and ground, or ECM harness connector and ground.
      DTC A/F sensor 1 Ground Continuity
      Bank Connector Terminal
      P0172 1 F89 1 Ground Not Existed
      2
      P0175 2 F90 1
      2
      DTC ECM Ground Continuity
      Bank Connector Terminal
      P0172 1 F92 79 Ground Not Existed
      74
      P0175 2 F92 69
      70
    6. Also check harness for short to power.

    Is the inspection result normal?

    YES 

    GO TO STEP 4  .

    NO 

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

  4. CHECK FUEL PRESSURE

    Check fuel pressure. Refer to WORK PROCEDURE .

    Is the inspection result normal?

    YES 

    GO TO STEP 5  .

    NO 

    Replace fuel filter and fuel pump assembly". Refer to REMOVAL AND INSTALLATION .

  5. CHECK MASS AIR FLOW SENSOR

    G-20 WITH CONSULT

    1. Install all removed parts.
    2. Check "MASS AIR FLOW" in "DATA MONITOR" mode with CONSULT.

      For specification, refer to MASS AIR FLOW SENSOR .

    NSM020 WITH GST

    1. Install all removed parts.
    2. Check mass air flow sensor signal in "Service $01" with GST.

      For specification, refer to MASS AIR FLOW SENSOR .

    Is the measurement value within the specification?

    YES 

    GO TO STEP 6  .

    NO 

    Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or grounds. Refer to DIAGNOSIS PROCEDURE .

  6. CHECK FUNCTION OF FUEL INJECTOR

    G-20 WITH CONSULT

    1. Start engine.
    2. Perform "POWER BALANCE" in "ACTIVE TEST" mode with CONSULT.
    3. Check that each circuit produces a momentary engine speed drop.

    G-21 WITHOUT CONSULT

    1. Start engine and let it idle.
    2. Listen to each fuel injector operating sound.
      G04812223Courtesy of NISSAN NORTH AMERICA, INC.
      Clicking sound should be heard.

    Is the inspection result normal?

    YES 

    GO TO STEP 7  .

    NO 

    Perform trouble diagnosis for fuel injector, refer to DIAGNOSIS PROCEDURE .

  7. CHECK INTERMITTENT INCIDENT

    Refer to INTERMITTENT INCIDENT .

    Is the inspection result normal?

    YES 

    Replace fuel injector. Refer to REMOVAL AND INSTALLATION .

    NO 

    Repair or replace malfunctioning part.

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