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Home › Nissan-Datsun › 2005 › Pathfinder LE, RWD › Repair and Diagnosis › Engine Performance › Engine Control System › DTC P0139, P0159: Ho2S2 › Diagnostic Procedure

Diagnostic Procedure

  1. CHECK GROUND CONNECTIONS 
    1. Turn ignition switch OFF.
    2. Loosen and retighten three ground screws on the body. Refer to GROUND INSPECTION .
      Fig 1: Tightening Ground Screws On Body
      G02431744Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    • OK: GO TO 2.
    • NG: Repair or replace ground connections.
  2. 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".
    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 2: CONSULT-II Display - Work Support Mode
      G02431745Courtesy 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, and restart and run engine for at least 5 seconds at idle speed.
    4. Stop engine and reconnect mass air flow sensor harness connector.
    5. Make sure DTC P0102 is displayed.
    6. Erase the DTC memory. Refer to HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION .
    7. Make sure DTC P0000 is displayed.
    8. 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: Locating Mass Air Flow Sensor
      G02431746Courtesy of NISSAN MOTOR CO., U.S.A.

    Yes or No 

  3. CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT 
    1. Turn ignition switch OFF.
    2. Disconnect heated oxygen sensor 2 harness connector.
      Fig 4: Locating Heated Oxygen Sensor 2 Harness Connectors
      G02431747Courtesy of NISSAN MOTOR CO., U.S.A.
    3. Disconnect ECM harness connector.
    4. Check harness continuity between HO2S2 terminal 4 and ECM terminal 78.

      Refer to WIRING DIAGRAM .

      • Continuity should exist. 
    5. Also check harness for short to ground and 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 HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT 
    1. Check harness continuity between ECM terminal and HO2S2 terminal as follows.

      Refer to WIRING DIAGRAM .

      Fig 5: ECM Terminal And HO2S Terminal Reference Chart (1 Of 2)
      G02431748Courtesy of NISSAN MOTOR CO., U.S.A.
      • Continuity should exist. 
    2. Check harness continuity between the following terminals and ground.

      Refer to WIRING DIAGRAM .

      Fig 6: ECM Terminal And HO2S Terminal Reference Chart (2 Of 2)
      G02431749Courtesy of NISSAN MOTOR CO., U.S.A.
      • Continuity should not exist. 
    3. Also check harness for short to power.

    OK or NG 

    • OK: GO TO 5.
    • NG: Repair open circuit or short to ground or short to power in harness or connectors.
  5. CHECK HEATED OXYGEN SENSOR 2 

    Refer to COMPONENT INSPECTION .

    OK or NG 

    • OK: GO TO 6.
    • NG: Replace malfunctioning heated oxygen sensor 2.
  6. CHECK INTERMITTENT INCIDENT 

    Refer to TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT .

    • : INSPECTION END 
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