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Nissan Versa
 Sedan Service Manual
Engine » Engine control system (EC) » P0420 three way catalyst function
DTC Logic

DTC DETECTION LOGIC

The ECM monitors the switching frequency ratio of air fuel ratio (A/F) sensor 1 and heated oxygen sensor 2.

A three way catalyst (manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2.

As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase.

When the frequency ratio of air fuel ratio (A/F) sensor 1 and heated oxygen sensor 2 approaches a specified limit value, the three way catalyst (manifold) malfunction is diagnosed.

DTC DETECTION LOGIC

DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0420 Catalyst system efficiency below threshold
  • Three way catalyst (manifold) does not operate properly.
  • Three way catalyst (manifold) does not have enough oxygen storage capacity
  • Three way catalyst (manifold)
  • Exhaust tube
  • Intake air leaks
  • Fuel injector
  • Fuel injector leaks
  • Spark plug
  • Improper ignition timing

1.INSPECTION START

Do you have CONSULT?

YES >> GO TO 2.

NO >> GO TO 7.

2.PRECONDITIONING

If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.

  1. Turn ignition switch OFF and wait at least 10 seconds.
  2. Turn ignition switch ON.
  3. Turn ignition switch OFF and wait at least 10 seconds.

TESTING CONDITION: Do not hold engine speed for more than the specified minutes below.

>> GO TO 3.

3.PERFORM DTC CONFIRMATION PROCEDUREI

With CONSULT

  1. Start engine and warm it up to the normal operating temperature.
  2. Turn ignition switch OFF and wait at least 10 seconds.
  3. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
  4. Let engine idle for 1 minute.
  5. Select "COOLAN TEMP/S" in "DATA MONITOR" mode with CONSULT.
  6. Make sure that "COOLAN TEMP/S" indicates more than 70C (158F).

    If not, warm up engine and go to next step when "COOLAN TEMP/S" indication reaches to 70C (158F).

  7. Open engine hood.
  8. Select "DTC & SRT CONFIRMATION" then "SRT WORK SUPPORT" mode with CONSULT.
  9. Rev engine up to 2,000 to 3,000 rpm and hold it for 3 consecutive minutes then release the accelerator pedal completely.
  10. Check the indication of "CATALYST".

Which is displayed on CONSULT screen?

CMPLT>> GO TO 6.

INCMP >> GO TO 4.

4.PERFORM DTC CONFIRMATION PROCEDUREII

  1. Wait 5 seconds at idle.
  2. Rev engine up to 2,000 to 3,000 rpm and maintain it until "INCMP" of "CATALYST" changes to "CMPLT" (It will take approximately 5 minutes).

Does the indication change to "CMPLT"?

YES >> GO TO 6.

NO >> GO TO 5.

5.PERFORM DTC CONFIRMATION PROCEDURE AGAIN

  1. Stop engine and cool it down to less than 70C (158F).
  2. Perform DTC CONFIRMATION PROCEDURE again.

>> GO TO 3.

6.PERFORM DTC CONFIRMATION PROCEDUREIII

Check 1st trip DTC.

Is 1st trip DTC detected?

YES >> Go to EC, "Diagnosis Procedure".

NO >> INSPECTION END

7.PERFORM COMPONENT FUNCTION CHECK

Perform component function check. Refer to EC, "Component Function Check".

NOTE: Use component function check to check the overall function of the three way catalyst (manifold). During this check, a 1st trip DTC might not be confirmed.

Is the inspection result normal?

YES >> INSPECTION END

NO >> Go to EC, "Diagnosis Procedure".

    More about «P0420 three way catalyst function»:

    DTC Logic

    Component Function Check

    Diagnosis Procedure

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