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Home >> Nissan-Datsun >> 2004 >> Frontier Base, Automatic >> Repair and Diagnosis >> Engine Performance >> Engine Control System - KA24DE >> 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 

    1. OK : GO TO 2.
    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 three way catalyst (manifold).
    Fig 1: Checking Exhaust Gas Leak
    G00857130Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    1. OK : GO TO 3.
    2. NG : Repair or replace.
  3. CHECK INTAKE AIR LEAK 

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

    OK or NG 

    1. OK : GO TO 4.
    2. NG : Repair or replace.
  4. CHECK IGNITION TIMING 
    1. Check the following items. Refer to Basic Inspection .
    Fig 2: Specification Chart
    G00857131Courtesy of NISSAN MOTOR CO., U.S.A.

    OK or NG 

    1. OK : GO TO 5.
    2. NG : Adjust ignition timing.
  5. CHECK INJECTORS 
    1. Refer to WIRING DIAGRAM  for injectors, WIRING DIAGRAM .
    2. Stop engine and then turn ignition switch ON.
    3. Check voltage between ECM terminals 102, 104, 109 and 111 and ground with CONSULT-II or tester.

      Battery voltage should exist. 

    OK or NG 

    1. OK : GO TO 6.
    2. NG : Perform DIAGNOSTIC PROCEDURE .
    Fig 3: Checking Voltage Between ECM Terminals And Ground
    G00857132Courtesy of NISSAN MOTOR CO., U.S.A.
  6. CHECK IGNITION SPARK 
    1. Disconnect ignition wire from spark plug.
    2. Connect a known good spark plug to the ignition wire.
    3. Place end of spark plug against a suitable ground and crank engine.
    4. Check for spark.

    OK or NG 

    1. OK : GO TO  8.
    2. NG : GO TO 7.
    Fig 4: Checking Spark Of Spark Plug
    G00857133Courtesy of NISSAN MOTOR CO., U.S.A.
  7. CHECK IGNITION WIRES 
    1. Inspect wires for cracks, damage, burned terminals and for improper fit.
    2. Measure the resistance of wires to their distributor cap terminal.

      Move each wire while testing to check for intermittent breaks.

      Resistance : 13.6 - 18.4 kΩ/m (4.15 - 5.61 kΩ/ft) at 25°C (77°F) 

      If the resistance exceeds the above specification, inspect ignition wire to distributor cap connection. Clean connection or replace the ignition wire with a new one.

    OK or NG 

    1. OK : Check ignition coil, power transistor and their circuits. Refer to IGNITION SIGNAL .
    2. NG : Replace.
    Fig 5: Checking Ignition Wires
    G00857134Courtesy of NISSAN MOTOR CO., U.S.A.
  8. CHECK INJECTOR 
    1. Turn ignition switch OFF.
    2. Remove injector assembly.

      Keep fuel hose and all injectors connected to injector gallery.

    3. Disconnect camshaft position sensor harness connector.
    4. Turn ignition switch "ON".

      Make sure fuel does not drip from injector.

    OK or NG 

    1. OK (Does not drip.) : GO TO 9.
    2. NG (Drips.) : Replace the injector(s) from which fuel is dripping.
  9. CHECK INTERMITTENT INCIDENT 

    Perform TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT .

    1. Trouble is fixed: INSPECTION END. 
    2. Trouble is not fixed: Replace three way catalyst (manifold).