our 2000 SSEi displayed this on the DIC about a month ago, alongwith a SES light so we took it in to get scanned. The scanner confirmed the "check gas cap" message so we bought a new gas cap and go the SES light cleared.. it stayed away for a month but now the problem is back. The SES light isnt' on (yet) but the "check gas cap" is.. any ideas?

Did you make sure you put the gas cap on after filling up with gas :P

Actually i'm just kidding and don't really have any idea. I've never heard of a gas cap going bad.

I have....If the seal is damaged in even the slightest way, it will set off the CES light!

the gas cap'* been replaced and the problem is still there.. is it a problem with the car'* seal and no the gas cap itself?

Wow, I never heard of that kind of error message.

the 2000+ models with the driver information center tell you all kinds of things. even tells you "tire pressure low."

That'* pretty sweet. I guess it'* nice in case you accidently forget to put the gas cap on before you leave the gas station.

I had that displayed on the DIC one time before also, but without the SES light. I re-seated the gas cap and it never displayed again. It seemed like just a one time glitch.

About every car nowdays is made to have a 'sealed' pressurized fuel system,....several people I know(on different cars)have in some way or another failed to tighten on the gas filler cap,and the code will show up and/or the car will run like crap until the gas cap is taken care of.......

In one of the latest Onstar commercial, a woman calls in and says the SES light came on and the Onstar rep was able to diagnoseit via the satellite. The Onstar rep told her she should check her gas cap.