:crying:
You are lucky for sure. For the second time, my Avalanche a few months ago came up with a similar code and the dash message.........."tighten fuel cap". Well, a few yrs ago, with the same scenario, I bought a new gas cap. Problem not solved. There are two other (potential) culprits.....the vent valve solenoid and also the canister. One is under the truck close to the tank and the other is on top of the engine block.
The event a few yrs ago, the gas cap did not solve, but the solenoid under the truck replaced did solve it. So for about $30--$40, I was good to go. Not the case on my most recent repeat episode. I ignored (replace the gas cap), and went with a new solenoid......didn't solve it. So I went with the other deal on top of engine.......didn't solve it........So, as a last result (after applying vasoline to the cap gasket.....) I bought a new one again.:frown2: Didnt help.
There is such a thing known as a "smoke test".........they inject smoke into the system and look for where it comes out/shows up. In my case, right on top side of gas tank. So removal of tank and subsequent replacement of the "vent" line (chewed up by squirrels):frown2::frown2::frown2

cost me close to $500 overall.:|