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Home >> Nissan-Datsun >> 2016 >> Sentra S, Automatic CVT Trans >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (DTCS) (2 Of 3) >> DTC/Circuit Diagnosis >> DTC P0420: Three Way Catalyst Function >> Diagnosis Procedure >> Diagnostic Test

Diagnostic Test

  1. CHECK EXHAUST SYSTEM

    Visually check exhaust tubes and muffler for dent.

    Is the inspection result normal?

    YES 

    GO TO STEP 2  .

    NO 

    Repair or replace error-detected parts.

  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: Checking Exhaust Gas Leak
      G04191081Courtesy of NISSAN NORTH AMERICA, INC.

    Is exhaust gas leak detected?

    YES 

    Repair or replace error-detected parts.

    NO 

    GO TO STEP 3  .

  3. CHECK INTAKE AIR LEAK

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

    Is intake air leak detected?

    YES 

    Repair or replace error-detected parts.

    NO 

    GO TO STEP 4  .

  4. CHECK IGNITION TIMING AND IDLE SPEED

    Check the following items.

    Is the inspection result normal?

    YES 

    GO TO STEP 5  .

    NO 

    Perform "BASIC INSPECTION". Refer to WORK PROCEDURE .

  5. CHECK FUEL INJECTOR

    Check the fuel injector. Refer to COMPONENT FUNCTION CHECK .

    Is the inspection result normal?

    YES 

    GO TO STEP 6  .

    NO 

    Perform DIAGNOSIS PROCEDURE .

  6. CHECK FUNCTION OF IGNITION COIL-1

    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 in IPDM E/R to release fuel pressure.
      NOTE:

      Do not use CONSULT to release fuel pressure, or fuel pressure applies again during the following procedure.

    3. Start engine.
    4. After engine stalls, crank it two or three times to release all fuel pressure.
    5. Turn ignition switch OFF.
    6. Remove all ignition coil harness connectors to avoid the electrical discharge from the ignition coils.
    7. Remove ignition coil and spark plug of the cylinder to be checked.
    8. Crank engine for 5 seconds or more to remove combustion gas in the cylinder.
    9. Connect spark plug and harness connector to ignition coil.
    10. Fix ignition coil using a rope etc. with gap of 13 - 17 mm (0.52 - 0.66 in) between the edge of the spark plug and grounded metal portion as shown in the figure.
      Fig 2: Checking For Spark
      G04886523Courtesy of NISSAN NORTH AMERICA, INC.
    11. Crank engine for about 3 seconds, and check whether spark is generated between the spark plug and the grounded metal portion.
      Spark should be generated.
      CAUTION:
      • Do not approach to the spark plug and the ignition coil within 50 cm (19.7 in). Be careful not to get an electrical shock while checking, because the electrical discharge voltage becomes 20 kV or more.
      • It might cause to damage the ignition coil if the gap of more than 17 mm (0.66 in) is taken.
      NOTE:

      When the gap is less than 13 mm (0.52 in), the spark might be generated even if the coil is malfunctioning. 

    Is the inspection result normal?

    YES 

    GO TO STEP   10  .

    NO 

    GO TO STEP 7  .

  7. CHECK FUNCTION OF IGNITION COIL-2

    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.

    Is the inspection result normal?

    YES 

    GO TO STEP 8  .

    NO 

    Check ignition coil, power transistor and their circuits. Refer to DIAGNOSIS PROCEDURE .

  8. CHECK SPARK PLUG

    Check the initial spark plug for fouling, etc. Refer to INSPECTION .

    Fig 3: Checking Spark Plug For Fouling
    G04185314Courtesy of NISSAN NORTH AMERICA, INC.

    Is the inspection result normal?

    YES 

    Replace spark plug(s) with standard type one(s). For spark plug type, refer to SPARK PLUG .

    NO 

    1. Repair or clean spark plug. Refer to REMOVAL AND INSTALLATION .
    2. GO TO STEP 9  .

  9. CHECK FUNCTION OF IGNITION COIL-3

    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.

    Is the inspection result normal?

    YES 

    INSPECTION END

    NO 

    Replace spark plug(s) with standard type one(s). For spark plug type, refer to SPARK PLUG .

  10. CHECK FUEL INJECTOR

    1. Turn ignition switch OFF.
    2. Remove fuel injector assembly. Refer to REMOVAL AND INSTALLATION .

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

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

    Does fuel drip from fuel injector?

    YES 

    GO TO STEP 11  .

    NO 

    Replace the fuel injector(s) from which fuel is dripping. Refer to REMOVAL AND INSTALLATION .

  11. CHECK INTERMITTENT INCIDENT

    Check intermittent incident. Refer to INTERMITTENT INCIDENT .

    Is the trouble fixed?

    YES 

    INSPECTION END

    NO 

    Replace three way catalyst assembly. Refer to EXPLODED VIEW .

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