LOL EVAP vent solenoid. Literally a 10min job to replace the part. Part cost is like $25 or so for AC Delco. Don't get it done by dealer. They charge like an hour labour haha.
IIRC to replace it you have to remove the bolt on the left side of the EVAP canister thing at the back by the rear axle to rotate it down, then you undo a screw/bolt that holds the solenoid in, and it unclips and comes out, then reverse for install.
Crude explanation, but nothing crazy. It may go again shortly after you replace it as well since there can be crap in the lines.
Hope this helps.
2008 Cobalt LT // 2.2L Supercharged w/3.1 GM stage 2 pulley