I kept getting the check engine light and tighten gas cap. Paid dealership (almost $200 including labor) for a new gas cap. Now almost a year later getting same check engine light and tighten gas cap. This time they're saying I need to replace evap vent solenoid for $130. It seems like a lot of the issues with this car are the same. GM should step up and solve them.
Clean off the inside of the gas cap with WD40. After I got all of this dirt out, the "Tighten Gas Cap" error never came back up. Air must have been getting into the system and reducing the vacuum pressure for the gas going to the engine.
P0449 code!! I've owned this vehicle since it came off the line. Very few problems,but I don't drive it like its a race car. if you're having an issue with your check engine light due to p0449 code then it can be a few things. 1 a bad gas cap which happens all of the time it is a common issue. 2 a small solenoid in the front of the engine next to the throttle body can get clogged up or just go bad. 3 a small canister behind the driver rear wheel can go bad and also cause these problems. Vent solenoid, purge valve, vent valve, look these up for the impala.