Toyota
Nissan Versa
 Sedan Service Manual
Engine » Engine control system (EC) » P0420 three way catalyst function
Diagnosis Procedure

1.CHECK EXHAUST SYSTEM

Visually check exhaust tubes and muffler for dent.

Is the inspection result normal?

YES >> GO TO 2.

NO >> 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).

CHECK EXHAUST GAS LEAK

Is exhaust gas leak detected?

YES >> Repair or replace.

NO >> GO TO 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.

NO >> GO TO 4.

4.CHECK IGNITION TIMING AND IDLE SPEED

Check the following items. Refer to EC, "Work Procedure".

For specification, refer to EC, "Ignition Timing" For specification, refer to EC, "Idle Speed".

Is the inspection result normal?

YES >> GO TO 5.

NO >> Follow the EC, "Work Procedure".

5.CHECK FUEL INJECTOR

  1. Stop engine and then turn ignition switch ON.
  2. Check the voltage between ECM harness connector and ground. 

Is the inspection result normal?

YES >> GO TO 6.

NO >> Perform EC, "Diagnosis Procedure".

6.CHECK FUNCTION OF IGNITION COILI

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.
  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.

CHECK FUNCTION OF IGNITION COILI

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 10.

NO >> GO TO 7.

7.CHECK FUNCTION OF IGNITION COILII

  1. Turn ignition switch OFF.

  2. Disconnect spark plug and connect a knowngood spark plug.

  3. Crank engine for about 3 seconds, and recheck whether spark is generated between the spark plug and the grounded metal portion.

Is the inspection result normal?

YES >> GO TO 8.

NO >> Check ignition coil, power transistor and their circuits. Refer to EC, "Diagnosis Procedure".

8.CHECK SPARK PLUG

Check the initial spark plug for fouling, etc.

Is the inspection result normal?

YES >> Replace spark plug(s) with standard type one(s). For spark plug type, refer to EM, "Spark Plug".

NO >> Repair or clean spark plug. Then GO TO 9

CHECK SPARK PLUG

9.CHECK FUNCTION OF IGNITION COILIII

  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.

Is the inspection result normal?

YES >> INSPECTION END

NO >> Replace spark plug(s) with standard type one(s). For spark plug type, refer to EM, "Spark Plug".

10.CHECK FUEL INJECTOR

  1. Turn ignition switch OFF.
  2. Remove fuel injector assembly.

    Refer to EM37, "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 11.

NO >> Replace the fuel injector(s) from which fuel is dripping. Refer to EM, "Removal and Installation".

11.CHECK INTERMITTENT INCIDENT

Refer to GI, "Intermittent Incident".

Is the trouble fixed?

YES >> INSPECTION END

NO >> Replace three way catalyst assembly. Refer to EX, "Exploded View".

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