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Home >> Nissan-Datsun >> 2004 >> Sentra SE-R >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Qr25DE >> DTC P0139: Ho2S2 >> Diagnostic Procedure
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Diagnostic Procedure

  1. RETIGHTEN GROUND SCREWS 
    1. Turn ignition switch OFF.
    2. Loosen and retighten engine ground screws.
      Fig 1: Identifying Engine Ground
      G00777074Courtesy of NISSAN MOTOR CO., U.S.A.
      1. GO TO 2.
  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 or P0172 detected? 

      Is it difficult to start engine? 

      Fig 2: Selecting SELF-LEARNING CONT With Consult-II
      G00777075Courtesy 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. Fig 3: Identifying Mass Air Flow Sensor Harness Connector
      G00777076Courtesy of NISSAN MOTOR CO., U.S.A.
    5. Make sure that DTC P0102 is displayed.
    6. Erase the DTC memory. Refer to "HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION ".
    7. Make sure that DTC P0000 is displayed.
    8. Run engine for at least 10 minutes at idle speed.

      Is the 1st trip DTC P0171 or P0172 detected? 

      Is it difficult to start engine? 

    Yes or No 

    1. Yes: perform trouble diagnosis for DTC P0171 or P0172. Refer to DTC P0171 FUEL INJECTION SYSTEM FUNCTION  or DTC P0172 FUEL INJECTION SYSTEM FUNCTION .
    2. No: GO TO 3.
  3. CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT 
    1. Turn ignition switch OFF.
    2. Disconnect heated oxygen sensor 2 harness connector.
    3. Disconnect ECM harness connector.
    4. Check harness continuity between ECM terminal 78 and HO2S2 terminal 4.

      Refer to WIRING DIAGRAM .

      Continuity should exist. 

    5. Also check harness for short to ground and short to power.
    Fig 4: Disconnecting Heated Oxygen Sensor 2 Harness Connector
    G00777077Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    1. OK: GO TO 4.
    2. 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 74 and HO2S2 terminal 1. Refer to WIRING DIAGRAM .

      Continuity should exist. 

    2. Check harness continuity between ECM terminal 74 or HO2S2 terminal 1 and ground. Refer to WIRING DIAGRAM .

      Continuity should not exist. 

    3. Also check harness for short to power.

    OK or NG 

    1. OK: GO TO 5.
    2. 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 

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

    Refer to "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT ".

    1. INSPECTION END 
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