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Home › Infiniti › 2008 › QX56 AWD › Repair and Diagnosis › Engine Performance › Engine Control Systems › Engine Control System - DTCS P1148 To P2A03 › DTC P2A00, P2A03: A/F Sensor 1 › Diagnosis Procedure

Diagnosis Procedure

  1. CHECK GROUND CONNECTIONS
    1. Turn ignition switch OFF.
    2. Loosen and retighten two ground screws on the body.

      Refer to "GROUND INSPECTION ".

      Fig 1: Identifying Body Ground Screw
      G05739699Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO 2.

    NG: Repair or replace ground connections.

  2. RETIGHTEN A/F SENSOR 1
    1. Loosen and retighten the A/F sensor 1.
      Fig 2: Identifying Retighten A/F Sensor 1
      G05739700Courtesy of NISSAN MOTOR CO., U.S.A.

      Tightening torque: 50 N-m (5.1 kg-m, 37 ft-lb) 

      GO TO 3.

  3. CHECK FOR INTAKE AIR LEAK
    1. Start engine and run it at idle.
    2. Listen for an intake air leak after the mass air flow sensor.

    OK or NG 

    OK: GO TO 4.

    NG: Repair or replace.

  4. CLEAR THE SELF-LEARNING DATA

    With CONSULT-III 

    1. Start engine and warm it up to normal operating temperature.
    2. Select "SELF-LEARNING CONT" in "WORK SUPPORT" mode with CONSULT-III.
    3. Clear the self-learning control coefficient by touching "CLEAR".
    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? 

    Without CONSULT-III 

    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 "DTC INDEX ".
    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? 

      Fig 3: Identifying Mass Air Flow (MAF) Sensor Harness Connector
      G05739701Courtesy of NISSAN MOTOR CO., U.S.A.

    Yes or No 

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

    No: GO TO 5.

  5. CHECK HARNESS CONNECTOR
    1. Turn ignition switch OFF.
    2. Disconnect A/F sensor 1 harness connector.
      Fig 4: Identifying A/F Sensor 1 Harness Connector
      G05739702Courtesy of NISSAN MOTOR CO., U.S.A.
    3. Check harness connector for water.

      Water should not exit. 

    OK or NG 

    OK: GO TO 6.

    NG: Repair or replace harness connector.

  6. CHECK A/F SENSOR 1 POWER SUPPLY CIRCUIT
    1. Turn ignition switch ON.
    2. Check voltage between A/F sensor 1 terminal 4 and ground with CONSULT-III or tester.

      Voltage: Battery voltage 

    OK or NG 

    OK: GO TO  8.

    NG: GO TO 7.

    Fig 5: Checking Voltage Between A/F Sensor 1 Terminal 4 And Ground
    G05739703Courtesy of NISSAN MOTOR CO., U.S.A.
  7. DETECT MALFUNCTIONING PART

    Check the following.

    • Harness connectors E5, F14
    • IPDM E/R harness connector E119
    • 15A 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 .

      CONTINUITY REFERENCE CHART

        A/F sensor 1 terminal ECM terminal
      Bank1 1 35
      2 56
      Bank 2 1 16
      2 75

      Continuity should exist. 

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

      Refer to WIRING DIAGRAM .

      CONTINUITY REFERENCE CHART

      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. 

    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 A/F SENSOR 1 HEATER

    Refer to "COMPONENT INSPECTION ".

    OK or NG 

    OK: GO TO 10.

    NG: GO TO  11.

  10. CHECK INTERMITTENT INCIDENT

    Perform "HOW TO CHECK TERMINAL " and "INTERMITTENT INCIDENT ".

    OK or NG 

    OK: GO TO 11.

    NG: Repair or replace.

  11. REPLACE AIR FUEL RATIO (A/F) SENSOR 1

    Replace malfunctioning air fuel ratio (A/F) sensor 1.

    CAUTION:
    • Discard any A/F sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.
    • Before installing new A/F sensor, clean exhaust system threads using Oxygen Sensor Thread Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.

    GO TO 12.

  12. CONFIRM A/F ADJUSTMENT DATA
    1. Turn ignition switch OFF and then ON.
    2. Select "A/F ADJ-B1" and "" in "DATA MONITOR" mode with CONSULT-III.
    3. Make sure that "0.000" is displayed on CONSULT-III screen.

    OK or NG 

    OK: INSPECTION END 

    NG: GO TO 13.

  13. CLEAR THE SELF-LEARNING DATA

    With CONSULT-III 

    1. Start engine and warm it up to normal operating temperature.
    2. Select "SELF-LEARNING CONT" in "WORK SUPPORT" mode with CONSULT-III.
    3. Clear the self-learning control coefficient by touching "CLEAR".

    Without CONSULT-III 

    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 "MALFUNCTION INDICATOR LAMP (MIL) ".
    8. Make sure DTC P0000 is displayed.

      GO TO 14.

      Fig 6: Identifying Mass Air Flow (MAF) Sensor Harness Connector
      G05739704Courtesy of NISSAN MOTOR CO., U.S.A.
  14. CONFIRM A/F ADJUSTMENT DATA
    1. Turn ignition switch OFF and then ON.
    2. Select "A/F ADJ-B1" and "A/F ADJ-B2" in "DATA MONITOR" mode with CONSULT-III.
    3. Make sure that "0.000" is displayed on CONSULT-III screen.

      INSPECTION END 

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