I literally JUST bought this 2007 LTZ Avalanche black on black and have only owned it less than a week and I get this check engine code. w-t-f. I did a visual inspection of some of the system that I think was related to it. Hoses looked fine. I took off the gas cap and inspected it, and it appeared almost new. However I looked down into the gas fill hose area directly where you would put the fill hose and the metal flap doesn't seem to close all the way. Correct me if I am wrong, but isn't that metal flap inside the fill hose supposed to be 100% closed and couldn't that be my gross evap leak? Is this a common problem? If so any idea what part # I would need to fix it and how I could go about getting it done? Certainly hope I don't have to drop the gas tank to do it! Thanks guys.