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Nissan Repair/nissan codes


I have 4 codes from emissions testing center, P0450, P0440, P0446, P1447. What could this possibly mean, and what would be possible remedy. Thank Calvin, oh it is a 1996 Nissan.

Hi Sam -

These codes seem to be a defective EEC (Evaporative Emission Control) Canister.
However there are a few things you can do first:

Disconnect the electrical connector and then apply and remove 12V power to the vent solenoid/valve. The difference between 12V applied and not applied should be the difference between not being able to blow through it and being able to. After testing at least 5 times, if it fails even once, replace the solenoid/valve.

If replacing solenoid/valve it is usually best to replace the canister as well as you might inadvertently break the canister while replacing the solenoid/valve. With many Nissan vehicles, it is almost impossible to not break the canister without using techniques involving unreasonably high fire hazard.
I also could be the gas cap not on tight. Have the codes removed and see if it comes back on after you tighten the cap.
To check the vent system the engine vacuum valve is opened at the same time as the charcoal filter vent valve is closed. This creates a vacuum in the gas tank and when the vacuum reaches a certain level, the vacuum valve closes and the vent valve opens and a timer is started. If there is a restriction in the vent valve or it doesn't operate electrically, the tank fails to re-pressurize within the correct time and you get a P0446.

Below are what I consider the possible causes of P0446 in the order of least likelihood (IMO) for a vehicle used in a high dust environment:
Electrical vent driver circuit in computer burned out (especially if the vent valve is shorted), electrical vacuum valve driver circuit burnt out, vent valve coil open or shorted, vacuum valve coil open or shorted, bad vacuum sensor in the gas tank, vent valve filter clogged with dust, charcoal cannister clogged with dust or residues.

Hope this helpa -

Nissan Repair

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Calvin Iwashita


All general car repairs for all models of vehicles, except technicals (overhauls) on A/C systems and transmissions.


16 years as a car mechanic from 1974 to 1990, and still repair cars on the side.


High School and college graduate

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