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Home >> Infiniti >> 2012 >> QX56 AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - DTCS P1550 To P2A03 >> DTC P2A00, P2A03: A/F Sensor 1 >> Diagnosis Procedure

Diagnosis Procedure

  1. RETIGHTEN A/F SENSOR 1 AND HEATED OXYGEN SENSOR 2

    Loosen and retighten the A/F sensor 1 and heated oxygen sensor 2. Refer to "EXPLODED VIEW ".

    : GO TO 2.

  2. CHECK FOR EXHAUST GAS LEAK
    1. Start engine and run it at idle.
    2. Listen for an exhaust gas leak before the three way catalyst 2.

    Is exhaust gas leak detected? 

    YES: Repair or replace.

    NO: GO TO 3.

  3. CHECK A/F SENSOR 1 CONNECTOR
    1. Disconnect A/F sensor 1 harness connector.
    2. Check that water is not inside connectors.

    Is the inspection result normal? 

    YES: GO TO 4.

    NO: Repair or replace harness connector.

  4. CHECK FOR INTAKE AIR LEAKAGE
    1. Reconnect A/F sensor 1 harness connector.
    2. Start engine and run it at idle.
    3. Listen for an intake air leakage after the mass air flow sensor.

    Is intake air leakage detected? 

    YES: Repair or replace malfunctioning part.

    NO: GO TO 5.

  5. CLEAR THE MIXTURE RATIO SELF-LEARNING VALUE
    1. Clear the mixture ratio self-learning value. Refer to "WORK PROCEDURE ".
    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 6.

  6. CHECK AIR FUEL RATIO SENSOR 1 POWER SUPPLY CIRCUIT
    1. Disconnect air fuel ratio (A/F) sensor 1 harness connector.
    2. Turn ignition switch ON.
    3. Check the voltage between A/F sensor 1 harness connector and ground.
    DTC A/F sensor 1 Ground Voltage
    Bank Connector terminal
    P2A00 1 F67 4 Ground 3.0 V
    P2A03 2 F68 4

    Is the inspection result normal? 

    YES: GO TO 7.

    NO: Repair open circuit, short to ground or short to power in harness or connectors.

  7. 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.
      DTC A/F sensor 1 ECM Continuity
      Bank Connector Terminal Connector terminal
      P2A00 1 F67 3 F110 88 Existed
      P2A03 2 F68 3 78
    4. Check the continuity between A/F sensor 1 harness connector and ground, or ECM harness connector and ground.
      DTC A/F sensor 1 ECM Ground Continuity
      Bank Connector Terminal Connector terminal
      P2A00 1 F67 3 F110 88 Ground Not existed
      P2A03 2 F68 3 78
    5. Also check harness for short to power.

    Is the inspection result normal? 

    YES: GO TO 8.

    NO: Repair open circuit, short to ground or short to power in harness or connectors.

  8. CHECK A/F SENSOR 1 GROUND 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.
      DTC A/F sensor 1 ECM Continuity
      Bank Connector Terminal Connector terminal
      P2A00 1 F67 6 F110 94 Existed
      P2A03 2 F68 6 74
    4. Also check harness for short to power.

    Is the inspection result normal? 

    YES: GO TO 9.

    NO: Repair open circuit, short to ground or short to power in harness or connectors.

  9. CHECK A/F SENSOR 1 HEATER

    Refer to "COMPONENT INSPECTION (A/F SENSOR 1 HEATER) ".

    Is the inspection result normal? 

    YES: GO TO  10.

    NO: GO TO  12.

  10. CHECK HEATED OXYGEN SENSOR 2

    Check heated oxygen sensor 2. Refer to "COMPONENT INSPECTION (HO2 SENSOR 2) ".

    Is the inspection result normal? 

    YES: GO TO 11.

    NO: Repair or replace malfunctioning part.

  11. CHECK INTERMITTENT INCIDENT

    Perform "INTERMITTENT INCIDENT ".

    Is the inspection result normal? 

    YES: GO TO 12.

    NO: Repair or replace malfunctioning part.

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

    Replace air fuel ratio (A/F) sensor 1. Refer to "EXPLODED VIEW ".

    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 [commercial service tool (J-43897-18 or J-43897-12)] and approved anti-seize lubricant (commercial service tool).

    Will CONSULT be used? 

    YES: GO TO 13.

    NO: GO TO  14.

  13. CONFIRM A/F ADJUSTMENT DATA

    WITH CONSULT

    1. Turn ignition switch ON.
    2. Select "A/F ADJ-B1" and "A/F ADJ-B2" in "DATA MONITOR" mode with CONSULT.
    3. Check that "0.000" is displayed on CONSULT screen.

    Is "0.000" displayed? 

    YES: INSPECTION END

    NO: GO TO 14.

  14. CLEAR THE MIXTURE RATIO SELF-LEARNING VALUE

    Clear the mixture ratio self-learning value. Refer to "WORK PROCEDURE ".

    Will CONSULT be used? 

    YES: GO TO 15.

    NO: INSPECTION END

  15. CONFIRM A/F ADJUSTMENT DATA

    WITH CONSULT

    1. Turn ignition switch ON.
    2. Select "A/F ADJ-B1" and "A/F ADJ-B2" in "DATA MONITOR" mode with CONSULT.
    3. Check that "0.000" is displayed on CONSULT screen.

    : INSPECTION END

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