I'm having a really difficult time here with the check engine light. Just finished changing the knock sensor and a coil pack for cylinder 6, drove and the light comes back on. this time its P0446. Bought a new dealer gas cap, cleared codes, light came back on, bought Vacuum valve which comes together with the charcoal canister, had it replaced, still comes back on. even the mechanic who did the repair is not sure what it is. tried clearing the codes a couple times still comes back on. Already spend $1000. Any help would be greatly appreciated.

Have you checked the hose behind the air filter box? I had the same code come on after I had an oil change. They must have checked the air filter and in doing so the hose became disconnected from the small tube down behind the air filter box. You can do a search on po446 and see what others say. Good luck hope this helps. Let us know how you make out.

thanks for the advice, there are no loose connections by the air filter. today I'll be under the car to make sure once again that there are no loose vacuum hoses. Is it just me or does staring at the check engine light while driving annoying and bothersome?