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Home >> Infiniti >> 2004 >> QX56 RWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System >> DTC P1279, P1289: A/F Sensor 1 >> Diagnostic Procedure
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Diagnostic Procedure

  1. CHECK GROUND CONNECTIONS 
    1. Turn ignition switch OFF.
    2. Loosen and retighten ground three screws on the body.
      Fig 1: Checking Ground Connections
      G02691775Courtesy of NISSAN MOTOR CO., U.S.A.

      Refer to GROUND INSPECTION .

    OK or NG

    OK: GO TO 2.

    NG: Repair or replace ground connections.

  2. RETIGHTEN A/F SENSOR 1 

    Loosen and retighten the A/F sensor 1.

    Fig 2: DTC P1279, P1289 Retightening A/F Sensor 1
    G02691776Courtesy of NISSAN MOTOR CO., U.S.A.

    Tightening torque: 40 - 60 N.m (4.1 - 6.1 kg.m, 30 - 44 ft.lb) 

    : GO TO 3.

  3. 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 3: DTC P1279, P1289 Checking Exhaust Gas Leak
      G02691777Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG

    OK: GO TO 4.

    NG: Repair or replace.

  4. CHECK FOR INTAKE AIR LEAK 

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

    OK or NG

    OK: GO TO 5.

    NG: Repair or replace.

  5. CLEAR THE SELF-LEARNING DATA 

    WITH CONSULT-II 

    1. Start engine and warm it up to normal operating temperature.
    2. Select "SELF-LEARNING CONT" in "WORK SUPPORT" mode with CONSULT-II.
    3. Clear the self-learning control coefficient by touching "CLEAR" or START".
    4. Run engine for at least 10 minutes at idle speed.

      Is the 1st trip DTC P0171, P0172 P0174 or P0175 detected? 

      Is it difficult to start engine? 

      Fig 4: DTC P1279, P1289 Selecting "SELF-LEARNING CONT" In "WORK SUPPORT" Mode With CONSULT-II
      G02691778Courtesy of NISSAN MOTOR CO., U.S.A.

    Without CONSULT-II 

    1. Start engine and warm it up to normal operating temperature.
    2. Turn ignition switch OFF.
    3. Disconnect mass air flow sensor harness connector.
    4. Restart engine and let it idle for at least 5 seconds.
    5. Stop engine and reconnect mass air flow sensor harness connector.
    6. Make sure DTC P0102 is displayed.
    7. Erase the DTC memory. Refer to HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION .
    8. Make sure DTC P0000 is displayed.
    9. Run engine for at least 10 minutes at idle speed.

      Is the 1st trip DTC P0171, P0172, P0174 or P0175 detected? 

      Is it difficult to start engine? 

    Yes or No

    Yes: Perform trouble diagnosis for DTC P0171, P0174 or P0172, P0175. Refer to DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION  or DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION .

    No: GO TO 6.

    Fig 5: Locating Mass Air Flow Sensor (With Intake Air Temperature Sensor)
    G02691779Courtesy of NISSAN MOTOR CO., U.S.A.
  6. CHECK A/F SENSOR 1 POWER SUPPLY CIRCUIT 
    1. Turn ignition switch OFF.
    2. Disconnect A/F sensor 1 harness connector.
      Fig 6: Identifying A/F Sensor 1 Harness Connectors
      G02691780Courtesy of NISSAN MOTOR CO., U.S.A.
    3. Turn ignition switch ON.
    4. Check voltage between A/F sensor 1 terminal 3 and ground with CONSULT-II or tester.

      Voltage: Battery voltage 

    OK or NG

    OK: GO TO  8.

    NG: GO TO 7.

    Fig 7: DTC P1279, P1289 Checking Voltage Between A/F Sensor 1 Terminal 3 & Ground
    G02691781Courtesy of NISSAN MOTOR CO., U.S.A.
  7. DETECT MALFUNCTIONING PART 

    Check the following.

    • Harness connectors E5, F14
    • IPDM E/R harness connector E119
    • 10A fuse
    • Harness for open or short between A/F sensor 1 and fuse

      : Repair or replace harness or connectors.

  8. CHECK A/F SENSOR 1 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT 
    1. Turn ignition switch OFF.
    2. Disconnect ECM harness connector.
    3. Check harness continuity between A/F sensor 1 terminal and ECM terminal as follows.

      Refer to Wiring Diagram.

      Fig 8: DTC P1279, P1289 Checking A/F Sensor 1 Input Signal Circuit Continuity Reference Table (1 Of 2)
      G02691782Courtesy of NISSAN MOTOR CO., U.S.A.

      Continuity should exist. 

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

      Refer to Wiring Diagram.

      Fig 9: DTC P1279, P1289 Checking A/F Sensor 1 Input Signal Circuit Continuity Reference Table (2 Of 2)
      G02691783Courtesy of NISSAN MOTOR CO., U.S.A.

      Continuity should not exist. 

    5. Also check harness for short to power.

    OK or NG

    OK: GO TO 9.

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

  9. CHECK AIR FUEL RATIO (A/F) SENSOR 1 HEATER 

    Refer to COMPONENT INSPECTION .

    OK or NG

    OK: GO TO 10.

    NG: Replace A/F sensor 1.

  10. CHECK MASS AIR FLOW SENSOR 

    Refer to COMPONENT INSPECTION .

    OK or NG

    OK: GO TO 11.

    NG: Replace mass air flow sensor.

  11. CHECK PCV VALVE 

    Refer to POSITIVE CRANKCASE VENTILATION .

    OK or NG

    OK: GO TO 12.

    NG: Repair or replace PCV valve.

  12. CHECK INTERMITTENT INCIDENT 

    Perform TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT .

    OK or NG

    OK: Replace A/F sensor 1.

    NG: Repair or replace.

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