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Home >> Nissan-Datsun >> 2004 >> Altima S, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 1183 (Engine Control System - DTCS U0101 To P0183 (VQ40DE)) >> DTC P0171, P0174: Fuel Injection System Function >> Diagnosis Procedure

Diagnosis Procedure

WARNING: This page is about a different car, the 2012 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK EXHAUST GAS LEAK
    1. Start engine and run it at idle.
    2. Listen for an exhaust gas leak before three way catalyst (manifold).
    Fig 1: Checking Exhaust Gas Leak
    G08170512Courtesy of NISSAN NORTH AMERICA, INC.

    OK or NG 

    OK: GO TO 2.

    NG: Repair or replace.

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

    OK or NG 

    OK: GO TO 3.

    NG: Repair or replace.

  3. CHECK A/F SENSOR 1 INPUT SIGNAL CIRCUIT
    1. Turn ignition switch OFF.
    2. Disconnect corresponding A/F sensor 1 harness connector.
      Fig 2: Identifying A/F Sensor 1 Harness Connector
      G08170513Courtesy of NISSAN NORTH AMERICA, INC.
    3. Disconnect ECM harness connector.
    4. Check harness continuity between A/F sensor 1 terminal and ECM terminal as follows. Refer to WIRING DIAGRAM .
        A/F sensor 1 terminal ECM terminal
      Bank 1 1 35
      2 56
      Bank 2 1 16
      2 75

      Continuity should exist  .

    5. Check harness continuity between the following terminals and ground. Refer to WIRING DIAGRAM .
      Bank 1 Bank 2
      A/F sensor 1 terminal ECM terminal A/F sensor 1 terminal ECM terminal
      1 35 1 16
      2 56 2 75

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

    OK or NG 

    OK (With CONSULT)>>GO TO  6.

    OK (Without CONSULT)>>GO TO  7.

    NG: GO TO 5.

  5. DETECT MALFUNCTIONING PART

    Check the following.

    Repair or replace.

  6. CHECK MASS AIR FLOW SENSOR

    With CONSULT 

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

    2.0 - 6.0 g/s: at idling 

    7.0 - 20.0 g/s: at 2, 500 RPM 

    OK or NG 

    OK: GO TO  8.

    NG: Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or ground. Refer to "COMPONENT DESCRIPTION ".

  7. CHECK MASS AIR FLOW SENSOR

    With GST 

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

    2.0 - 6.0 g/s: at idling 

    7.0 - 20.0 g/s: at 2, 500 RPM 

    OK or NG 

    OK (P0171)>>GO TO  9.

    OK (P0174)>>GO TO  11.

    NG: Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or ground. Refer to "COMPONENT DESCRIPTION ".

  8. CHECK FUNCTION OF FUEL INJECTOR

    With CONSULT 

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

    OK or NG 

    OK: GO TO  12.

    NG: Perform trouble diagnosis for FUEL INJECTOR, refer to "COMPONENT DESCRIPTION ".

  9. CHECK FUNCTION OF FUEL INJECTOR-I

    Without CONSULT 

    1. Stop engine.
    2. Disconnect harness connector F44 (3), F201 (1)
      Fig 3: Identifying Vacuum Tank And Harness Connectors
      G08170514Courtesy of NISSAN NORTH AMERICA, INC.
    3. Turn ignition switch ON.
    4. Check voltage between harness connector F44 terminal 3 and ground with CONSULT or tester.

      Voltage: Battery voltage 

    5. Turn ignition switch OFF.
    6. Disconnect ECM harness connector.
    7. Check harness continuity between harness connector F44 and ECM as follows.

      Refer to WIRING DIAGRAM .

      Fig 4: Checking Harness Continuity Between Harness Connector F44 And ECM
      G08170515Courtesy of NISSAN NORTH AMERICA, INC.
      Cylinder Harness connector F44 terminal ECM terminal
      1 2 23
      3 1 22
      5 4 21

      Continuity should exist  .

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

    OK or NG 

    OK: GO TO 10.

    NG: Perform trouble diagnosis for FUEL INJECTOR, refer to "COMPONENT DESCRIPTION ".

  10. CHECK FUNCTION OF FUEL INJECTOR-II

    Provide battery voltage between harness connector F201 as follows and then interrupt it. Listen to each fuel injector operating sound.

    Cylinder Harness connector F201 terminal
    (+) (-)
    1 3 2
    3 3 1
    5 3 4

    Operating sound should exist  .

    Fig 5: Applying Battery Voltage Between Harness Connector F101 Terminals
    G08170516Courtesy of NISSAN NORTH AMERICA, INC.

    OK or NG 

    OK: GO TO  12.

    NG: Perform trouble diagnosis for FUEL INJECTOR, refer to "COMPONENT DESCRIPTION ".

  11. CHECK FUNCTION OF FUEL INJECTOR
    1. Start engine.
    2. Listen to fuel injectors No. 2, No. 4, No. 6 operating sound.

    Clicking noise should exist  .

    Fig 6: Checking Fuel Injector Operating Sound
    G08170517Courtesy of NISSAN NORTH AMERICA, INC.

    OK or NG 

    OK: GO TO 12.

    NG: Perform trouble diagnosis for FUEL INJECTOR, refer to "COMPONENT DESCRIPTION ".

  12. CHECK FUEL INJECTOR
    1. Confirm that the engine is cooled down and there are no fire hazards near the vehicle.
    2. Turn ignition switch OFF.
    3. Disconnect all injector harness connectors.
    4. Remove fuel tube assembly. Refer to "REMOVAL AND INSTALLATION ".

      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 7: Checking Fuel Injector
    G08170518Courtesy of NISSAN NORTH AMERICA, INC.

    OK or NG 

    OK: GO TO 13.

    NG: Replace fuel injectors from which fuel does not spray out. Refer to "REMOVAL AND INSTALLATION ". Always replace O-ring with new ones.

  13. CHECK INTERMITTENT INCIDENT

    Refer to "INTERMITTENT INCIDENT ".

    >> INSPECTION END 

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