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Home >> Nissan-Datsun >> 2006 >> Sentra SE-R >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - DTCS P0137 To P0445 (Qr25DE) >> DTC P0420 Three Way Catalyst Function >> Diagnostic Procedure
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Diagnostic Procedure

  1. CHECK EXHAUST SYSTEM 

    Visually check exhaust tubes and muffler for dent.

    OK or NG 

    OK: GO TO  2.

    NG: Repair or replace.

  2. CHECK EXHAUST GAS LEAK 
    1. Start engine and run it at idle.
    2. Listen for an exhaust gas leak before the three way catalyst (manifold).
      Fig 1: Inspecting For Exhaust Gas Leaks
      G04191081Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO  3.

    NG: Repair or replace.

  3. CHECK INTAKE AIR LEAK 

    Listen for an intake air leak after the mass air flow sensor.

    OK or NG 

    OK: GO TO  4.

    NG: Repair or replace.

  4. CHECK IGNITION TIMING 

    Check for ignition timing. Refer to "BASIC INSPECTION ".

    ITEM SPECIFICATION

    Items Specifications
    Target idle speed A/T 700 +/- 50 rpm (in P or N position)
    M/T 700 +/- 50 rpm (in Neutral position)
    Ignition timing A/T 15 +/- 5° BTDC (in P or N position)
    M/T 15 +/- 5° BTDC (in Neutral position)

    OK or NG 

    OK: GO TO  5.

    NG: Follow the Basic Inspection.

  5. CHECK FUEL INJECTORS 
    1. Refer to Wiring Diagram for fuel injectors, WIRING DIAGRAM .
    2. Stop engine and then turn ignition switch ON.
    3. Check voltage between ECM terminals 22, 23, 41, 42 and ground with CONSULT-II or tester.

      Battery voltage should exist. 

    4. Fig 2: Checking ECM Voltage
      G04191937Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: GO TO  6.

    NG: Perform "DIAGNOSTIC PROCEDURE ".

  6. CHECK FUNCTION OF IGNITION COIL-I 
    CAUTION: Do the following procedure in the place where ventilation is good without the combustible.
    1. Turn ignition switch OFF.
    2. Remove fuel pump fuse located in fuse box to release fuel pressure.
      NOTE: Do not use CONSULT-II to release fuel pressure, or fuel pressure applies again during the following procedure.
    3. Fig 3: Removing Fuel Pump Fuse
      G04191938Courtesy of NISSAN MOTOR CO., U.S.A.
    4. Start engine.
    5. After engine stalls, crank it 2 or 3 times to release all fuel pressure.
    6. Turn ignition switch OFF.
    7. Remove all ignition coil harness connectors to avoid the electrical discharge from the ignition coils.
    8. Remove ignition coil and spark plug of the cylinder to be checked.
    9. Crank engine for 5 seconds or more to remove combustion gas in the cylinder.
    10. Connect spark plug and harness connector to ignition coil.
    11. Fix ignition coil using a rope etc. with gap of 13 - 17 mm between the edge of the spark plug and grounded metal portion as shown in the figure.
    12. Crank engine for about three seconds, and check whether spark is generated between the spark plug and the grounded metal portion.

      Spark should be generated. 

      Fig 4: Checking For Spark Between Spark Plug And Grounded Metal On Engine
      G04074892Courtesy of NISSAN MOTOR CO., U.S.A.
      CAUTION:
      • Do not approach to the spark plug and the ignition coil within 50cm. Be careful not to get an electrical shock while checking, because the electrical discharge voltage becomes 20kV or more.
      • It might cause to damage the ignition coil if the gap of more than 17 mm is taken.
      NOTE: When the gap is less than 13 mm, the spark might be generated even if the coil is malfunctioning.

    OK or NG 

    OK: GO TO  10.

    NG: GO TO  7.

  7. CHECK FUNCTION OF IGNITION COIL-II 
    1. Turn ignition switch OFF.
    2. Disconnect spark plug and connect a known-good spark plug.
    3. Crank engine for about 3 seconds, and recheck whether spark is generated between the spark plug and the grounded metal portion.

      Spark should be generated. 

    OK or NG 

    OK: GO TO  8.

    NG: Check ignition coil, power transistor and their circuits. Refer to "IGNITION SIGNAL ".

  8. CHECK SPARK PLUG 

    Check the initial spark plug for fouling, etc.

    Fig 5: Checking Initial Spark Plug
    G04185314Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    OK: Replace spark plug(s) with standard type one(s). For spark plug type, refer to "CHANGING SPARK PLUGS (DOUBLE PLATINUM - TIPPED TYPE) ".

    NG :

    1. Repair or clean sparkplug.
    2. GO TO  9.
  9. CHECK FUNCTION OF IGNITION COIL-III 
    1. Reconnect the initial spark plugs.
    2. Crank engine for about 3 seconds, and recheck whether spark is generated between the spark plug and the grounded portion.

      Spark should be generated. 

    OK or NG 

    OK: INSPECTION END 

    NG: Replace spark plug(s) with standard type one(s). For spark plug type, refer to "CHANGING SPARK PLUGS (DOUBLE PLATINUM - TIPPED TYPE) ".

  10. CHECK FUEL INJECTOR 
    1. Turn ignition switch OFF.
    2. Remove fuel tube assembly. Refer to "FUEL INJECTOR AND FUEL TUBE ".

      Keep fuel hose and all fuel injectors connected to fuel tube.

    3. Disconnect ignition coil assembly harness connector.
    4. Reconnect all fuel injector harness connectors.
    5. Turn ignition switch ON.

      Make sure fuel does not drip from fuel injector.

    OK or NG 

    OK (Does not drip): GO TO  11.

    NG (Drips): Replace the fuel injector(s) from which fuel is dripping.

  11. CHECK INTERMITTENT INCIDENT 

    Perform "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT ".

    Trouble is fixed: INSPECTION END 

    Trouble is not fixed: Replace three way catalyst (manifold).