About 10 days ago, the check engine (MIL) light came on on my 2007 LS as I came up to a stop sign. Twice before I've had the light come on with this car shortly after getting gas, and both times tightening the gas cap caused the light to go off on its own after a few days. Assuming this might be the case again, I tightened the gas cap when I got home. Light stayed on for the next several days, and remained on after filling up again a few days ago.

So today I borrowed a code reader and see that the car has code P0446, which is an "EVAP Vent System" code. My first question would be - if it was caused by just an intermittent issue, will this code reset itself after a certain period of time, or is this one that would stay on until manually reset? Secondly, if it is an ongoing problem, what is the most likely cause on a cobalt, and roughly how expensive of a repair is it (and is it something easy to access and fix/replace myself?).

Much thanks for any input.

 

A damaged EVAP vent solenoid valve
• A pinched EVAP vent hose
• A damaged EVAP canister

I would put money on the solenoid and its a cheap part and easily replaced.