I had this issue for a little while and I decided to consolidate all the info into 1 Post and a picture of what you need to replace it. If you have any questions just ask in this thread:
What you need:
AC DELCO 214-2149 [CANISTER PURGE SOLENOID VALVE]
-Brand new AC DELCO component with correct connector
-Replaces dealer part numbers: 25932571, 214-2149
-It started off as 'Tighten Gas Cap" on the DIC, As the solenoid valve was stuck open and would vent the tank so the computer thought the gas cap was loose. I got the solenoid unstuck but later it failed in the close position and would not vent when filling the tank. I too tried everything including turning the nozzle completely upside down but the nozzle would just click off. The day after I replaced it I was able to fill the tank as fast as the pump would go and the engine light went out a day or so later, Have not had the problem ever since.
-Problem seems to be solved, I replaced the evap solenoid the day before yesterday and now I can fill the tank as fast as the pump will go. It only cost me $28, The engine light has not shut off yet but that should resolve itself in a few days after I drive it around a bit.
-It connects to the charcoal canister under the rear by the gas tank, A lot of people refer to it as the evap valve or solenoid.
-You have to crawl under but its just above and infront of the rear axel.
-A screw driver to pry up on the tab in the middle of the bracket and the same with tabs on the hose to release it. Then slide the new part back in the bracket and bend the tab back to hold it and make the connections.
-About 15 minutes of your time and no gas leaking, Also easier to get to if you drop the spare tire.
Hope this helps everyone!
**********New updated part info*************
GM understands that this is an issue and this part has been updated with a new one that has hoses and moves the filter, but the new part costs $250-300 and is harder to install, and if you get this part it will last another 4-6 years (Which is when I don't plan on having same Tahoe)
I don't really have trouble filling my tank up. But it lets out a massive vacuum pressure release when I take the gas cap off. And my CEL is on. I was already in need of replacing my fuel filter. I'm thinking I may need to replace this guy as well. Thoughts?
New to the site but glad i found this topic, so my wife got the gas cap message on her 08 TAHOE, by googleing this issue i came across this siteand found some good info.
So i actually changed out the canister saturday, reset the cp and was hoping the message would not come back on along with the engine light, so this morning she texts me and says it came back! Dang it!
Should i also change the evap solenoid that sits on top of the manifold that othere seemed to have changed also? Please let me know, thanks/