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Nissan Froniter Help

I have a 2008 nissand frontier SE 4x4 with 71K on her. I’m getting two codes from my checking engine light P0455 and P0447. Any suggestions on where to start to fix this…the gas cap is new and tight.

thanks for your help

P0455=EVAP System Large Leak Detected.

P0447=Vent Control Valve Circuit Open.

I would check to see if the vent control valve is functioning.


This is a symptom caused when the owner consistently tops off the gas on every fill up. The cheapest solution is to not add any more gas when the pump handle clicks off, do not even round up to the next nickel. Just hang up the pump, put the cap back on and pay.

The gas tank needs to be able to breath air in as the gas is pumped out to prevent the formation of excess vacuum. And, when the gas expands due to heat or agitation, or when being filled, the tank needs the ability to breath out. There is a “fresh air line” that allows this. Its path includes an activated charcoal filter to capture the hydrocarbon molecules qas the tank breaths through ti, to prevent them from escaping. The tank can thus breath in and out without allowing hydrocarbon molecules to escape.

The Vent Valve, controlled via a solenoid by the ECU, closes the fresh air line when the engine is running sufficient to allow a pump to draw a modest vacuum in the tank specifically to prevent hydrocarbon molecules from escaping. A pressure sensor tells the ECU when and how much to open the valve to allow the tank to breath in when the vacuum exceeds a set limit.

If the vent valve doesn’t close properly, it leaves a leak path that does not allow the vacuum pump to maintain the proper modest vacuum in the gas tank’s air space. And you get the codes you listed. The “circuit” being referred to is the vapor path controlled by the valve.

Tester is right. But you’ll need a knowledgeable shop to confirm a diagnosis and fix it. We can’t do that from here.