Okay...a month or so ago I fueled up my 2005 Cobalt LS...It was driving fine. The next day I went to work at 6am and on the display it says "Check Fuel Cap". So I do. It seems fine. But I checked it a couple times just to make sure. Then my MIL light came on...so I checked the cap again...the light stayed on for a couple of days and I didn't notice that the gas was evaporating rapidly...maybe only slightly. Then I started it up one day and the MIL went off...which I thought strange. I was under the impression that it had to be cleared in order for that light to go off...but anyways I went out and bought a "BRAND NEW" fuel cap...yes I made sure that it was the correct one. I put it on and it seemed like all was well. A day later... "DING DING" and the display says "Check Fuel Cap"...I get out and check it thinking okay its a new cap maybe I didn't get it on just right...3 clicks of the cap later...Then the next day I get in and drive to work and it does it again. I'm like WTF by now, getting really pissed at it...the MIL comes back on...The thing is I can't tell if my gas is evaporating...it doesn't seem like it is...Could it be a touchy sensor? I can't afford to take it to a shop right now...Grr!

 

I had the same thing happen to me, but it turns out it wasnt the gas cap. I had a leak in one of the lines. But good news, if you have had the car less than 8 years/ and are under 80,000 miles, the dealership has to replace anything emissions related under that 8year/80K miles for free! My dealer did a PCM update first, then found the leak a week later when the light came on again.

 

yeahhhhh....I just hit the 82,000 mile mark....

 

Bah that sucks man! Can you smell gas from the cap area? If so the filler neck may have been bent. When they put my car on a rack, I could see that it was leaking onto the rear crossbar by the fuel control unit.