Tighten gas cap????

My 2006 chevy Impala reads "Tighten Gas Cap" on the dash. Also the engine light is showing. I bought several caps to no avail. What seems to be the problem?

Dealer or aftermarket caps?

It is possible that there is a gross EVAP leak not related to the gas cap but is the same symptom as a loose or missing gas cap. If this is the case you could put gas caps on until your blue in the face and never solve the issue.

do you have the engine light on also? i have an 06 SS and right after i got the tighten gascap warning my engine light came on which makes the car starter not work. i went to autozone and they said it was an evap leak at the gas cap so i went home disconnected the battery which reset the engine light and when i put the gas cap on my car i push in hard as i turn and i let it click several times and i havent had a problem in several months

another "solution" to the gas cap is to put vaseline on the rubber seal of the gas cap. sometimes the rubber gets dried out and doesn't seal properly. after that you would have to disconnect the battery to reset the system or take it in and get the engine light shut off.

I had the same problem as the OP.
I finally took it to the dealer. The trouble was NOT the gas cap (or it's replacement). There is a "Gross Evap Leak", and the solution was a Vent Solenoid located in the Fuel Tank. The part was $60, and the labor was $200.

Those are pretty common on the GM's.

My 2006 Impala has this and I just replaced the Canister Vent Solenoid. The next morning the check engine light came back on. When I checked the code, it said the same problem. What else could be wrong around the canister? LEaky hose probably?

I forget what GM's specifically have this but check the fuses to see if there is a dedicated fuse for the vent solenoid. If there is check to see if it is blown.