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Home >> Infiniti >> 2008 >> G35 Base >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Engine Control System - DTCS P0850 Through P2A03 >> DTC P2A00, P2A03: A/F Sensor 1 >> Diagnosis Procedure
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Diagnosis Procedure

  1. CHECK GROUND CONNECTION
    1. Turn ignition switch OFF.
    2. Check ground connection M95. Refer to Ground Inspection in "CIRCUIT INSPECTION ".

    Is the inspection result normal? 

    YES: GO TO 2.

    NO: Repair or replace ground connection.

  2. RETIGHTEN A/F SENSOR 1
    1. Loosen and retighten the A/F sensor 1.

      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.

    Is intake air leak detected? 

    YES: Repair or replace.

    NO: GO TO 4.

  4. CLEAR THE MIXTURE RATIO SELF-LEARNING VALUE
    1. Clear the mixture ratio self-learning value. Refer to "MIXTURE RATIO SELF-LEARNING VALUE CLEAR : SPECIAL REPAIR REQUIREMENT ".
    2. 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: Perform trouble diagnosis for DTC P0171, P0174 or P0172, P0175. Refer to "DIAGNOSIS PROCEDURE " or "DIAGNOSIS PROCEDURE ".

    NO: GO TO 5.

  5. CHECK HARNESS CONNECTOR
    1. Turn ignition switch OFF.
    2. Disconnect A/F sensor 1 harness connector.
    3. Check harness connector for water.

      Water should not exit. 

    Is the inspection result normal? 

    YES: GO TO 6.

    NO: Repair or replace harness connector.

  6. CHECK A/F SENSOR 1 POWER SUPPLY CIRCUIT
    1. Turn ignition switch ON.
    2. Check the voltage between A/F sensor 1 harness connector and ground.
      TERMINALS VOLTAGE REFERENCE

      DTC A/F sensor 1 Ground Voltage
      Bank Connector Terminal
      P2A00 1 F3 4 Ground Battery voltage
      P2A03 2 F20 4

    Is the inspection result normal? 

    YES: GO TO  8.

    NO: GO TO 7.

  7. DETECT MALFUNCTIONING PART

    Check the following.

    • Harness connectors E3, F1
    • IPDM E/R harness connector E7
    • 15A fuse (No. 46)
    • 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 the continuity between A/F sensor 1 harness connector and ECM harness connector.
      TERMINALS CONTINUITY REFERENCE

      DTC A/F sensor 1 ECM Continuity
      Bank Connector Terminal Connector Terminal
      P2A00 1 F3 1 F102 57 Existed
      2 61
      P2A03 2 F20 1 65
      2 66
    4. Check the continuity between A/F sensor 1 harness connector or ECM harness connector and ground.
      TERMINALS CONTINUITY REFERENCE

      DTC A/F sensor 1 ECM Ground Continuity
      Bank Connector Terminal Connector Terminal
      P2A00 1 F3 1 F102 57 Ground Not existed
      2 61
      P2A03 2 F20 1 65
      2 66
    5. Also check harness for short to power.

    Is the inspection result normal? 

    YES: GO TO 9.

    NO: 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 ".

    Is the inspection result normal? 

    YES: GO TO 10.

    NO: GO TO  11.

  10. CHECK INTERMITTENT INCIDENT

    Perform "INTERMITTENT INCIDENT ".

    Is the inspection result normal? 

    YES: GO TO 11.

    NO: Repair or replace.

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

    Replace 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.

    Do you have CONSULT-III? 

    YES: GO TO 12.

    NO: GO TO  13.

  12. CONFIRM A/F ADJUSTMENT DATA

    With CONSULT-III 

    1. Turn ignition switch 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.

    Is "0.000" displayed? 

    YES: INSPECTION END

    NO: GO TO 13.

  13. CLEAR THE MIXTURE RATIO SELF-LEARNING VALUE

    Clear the mixture ratio self-learning value. Refer to "MIXTURE RATIO SELF-LEARNING VALUE CLEAR : SPECIAL REPAIR REQUIREMENT ".

    Do you have CONSULT-III? 

    YES: GO TO 14.

    NO: INSPECTION END

  14. CONFIRM A/F ADJUSTMENT DATA

    With CONSULT-III 

    1. Turn ignition switch 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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