I took a quick corner this morning and the engine light popped on and won't shut-off. Called onStar and they said it was an "evaporation" something or other code and asked if I had gotten gas lately. They said to make sure the gas cap was tight (not kidding) and after 7 restarts if it doesn't turn-off, have it serviced.

Anyone else have something similar?

H3wannabe

Not an H3 but had the GF's car in for a check engine light Friday. The gas cap was exactly what it was. For some reason it wasn't sealing anymore so the check engine light came on.

It just shut-off by itself today.

H3wannabe

Per EPA regulations, your fuel system has been monitored for leakage of fumes (and gasoline too). The fuel system is closed to atmosphere and pressurized. To do this, the auto manufacturers install a pressure sensor in the fuel tank.
There are two codes I believe, one for a large pressure leak, one for a small pressure leak.
If the cap is not installed correctly, it can set a code after about 40 miles for a small pressure leak. I would guess, nine out of ten times on a new vehicle it is due to the gas cap not being installed correctly.
For those people who drive down the road with the gas cap flapping in the wind, while rubbing the paint of their vehicles, will get a large leak code.