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Home >> Infiniti >> 2010 >> M45 Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - DTCS P0171 To P0456 >> DTC P0171, P0174 Fuel Injection System Function >> Diagnosis Procedure
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Diagnosis Procedure

  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).
    Fig 1: Checking Exhaust Gas Leakage
    G04900287Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO 2.

    NG: Repair or replace malfunctioning part.

  2. CHECK FOR INTAKE AIR LEAKAGE
    1. Listen for an intake air leakage after mass air flow sensor.
    2. Check PCV hose connection.

    OK or NG 

    OK: GO TO 3.

    NG: Repair or replace malfunctioning part.

  3. CHECK AIR FUEL RATIO (A/F) SENSOR 1 INPUT SIGNAL CIRCUIT
    1. Turn ignition switch OFF.
    2. Disconnect corresponding air fuel ratio (A/F) sensor 1 harness connector.
      Fig 2: Identifying Air Fuel Ratio (A/F) Sensor 1 Harness Connector
      G06303122Courtesy of NISSAN MOTOR CO., U.S.A.
    3. Disconnect ECM harness connector.
    4. Check harness continuity between the following terminals.

      Refer to SYSTEM WIRING DIAGRAMS article.

      ECM CONNECTOR TERMINALS REFERENCE CHART

        A/F sensor 1 terminal ECM terminal
      Bank 1 1 16
      2 75
      5 35
      6 56
      Bank 2 1 76
      2 77
      5 57
      6 58

      Continuity should exist  .

    5. Check harness continuity between the following terminals and ground.

      Refer to SYSTEM WIRING DIAGRAMS article.

      ECM CONNECTOR TERMINALS REFERENCE CHART

      Bank 1 Bank 2
      A/F sensor 1 terminal ECM terminal A/F sensor 1 terminal ECM terminal
      1 16 1 76
      2 75 2 77
      5 35 5 57
      6 56 6 58

      Continuity should not exist  .

    6. Also check harness for short to power.

    OK or NG 

    OK: GO TO 4.

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

  4. CHECK FUEL PRESSURE
    1. Release fuel pressure to zero. Refer to "FUEL PRESSURE CHECK ".
    2. Install fuel pressure gauge and check fuel pressure. Refer to "FUEL PRESSURE CHECK ".

      At idling: Approximately 350 kPa (3.57 kg/cm 2  , 51 psi) 

    OK or NG 

    OK: GO TO  6.

    NG: GO TO 5.

  5. DETECT MALFUNCTIONING PART

    Check the following.

    • Fuel pump and circuit (Refer to "DIAGNOSIS PROCEDURE ".)
    • Fuel pressure regulator (Refer to "FUEL PRESSURE CHECK ".)
    • Fuel lines
    • Fuel filter for clogging

      Repair or replace malfunctioning part.

  6. CHECK MASS AIR FLOW SENSOR

    With CONSULT-III 

    1. Install all removed parts.
    2. Start engine and warm it up to normal operating temperature.
    3. Check "MASS AIR FLOW" in "DATA MONITOR" mode with CONSULT-III.

      2.0 - 6.0 g.m/sec: at idling 

      7.0 - 20.0 g.m/sec: at 2, 500 RPM 

    With GST 

    1. Install all removed parts.
    2. Start engine and warm it up to normal operating temperature.
    3. Check mass air flow sensor signal in Service $01 with GST.

      2.0 - 6.0 g.m/sec: at idling 

      7.0 - 20.0 g.m/sec: at 2, 500 RPM 

    OK or NG 

    OK (With CONSULT-III): GO TO 7.

    OK (Without CONSULT-III): GO TO  8.

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

  7. CHECK FUNCTION OF FUEL INJECTOR

    With CONSULT-III 

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

    OK or NG 

    OK: GO TO  9.

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

  8. CHECK FUNCTION OF FUEL INJECTOR

    Without CONSULT-III 

    Listen to each fuel injector operating sound.

    Operating sound should exist  .

    OK or NG 

    OK: GO TO 9.

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

    Fig 3: Checking Fuel Injector Operating Sound
    G04900354Courtesy of NISSAN MOTOR CO., U.S.A.
  9. CHECK FUEL INJECTOR
    1. Turn ignition switch OFF.
    2. Check that the engine is cooled down and there are no fire hazards near the vehicle.
    3. Disconnect all fuel injector harness connectors.
    4. Remove fuel tube assembly. Refer to "COMPONENT ".

      Keep fuel hose and all fuel injectors connected to fuel tube.

    5. For DTC P0171, reconnect fuel injector harness connectors on bank 1.

      For DTC P0174, reconnect fuel injector harness connectors on bank 2.

    6. Disconnect all ignition coil harness connectors.
    7. Prepare pans or saucers under each fuel injector.
    8. Crank engine for about 3 seconds.

      For DTC P0171, make sure that fuel sprays out from fuel injectors on bank 1.

      For DTC P0174, make sure that fuel sprays out from fuel injectors on bank 2.

      Fuel should be sprayed evenly for each fuel injector  .

    Fig 4: Checking Fuel Injectors Spray
    G04875113Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO 10.

    NG: Replace fuel injectors from which fuel does not spray out. Always replace O-ring with new ones.

  10. CHECK INTERMITTENT INCIDENT

    Refer to "DIAGNOSIS PROCEDURE ".

    INSPECTION END 

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