ok most of time its a fuel system issues a lot of the time go to fuel cap pull it off inspect the seal around the cap any tear or signs of wear. Replace if necessary. after 5 or 6 drive cycles it will turn off. if it comes on again or stays on, go to your local part store and have them read the code with the scanner. its free. you may have to replace the cap. They might also tell you its an o2 sensor, ask them to show you on the car where it is. then buy a 02 sensor and replace it your self. saving you about a $100. remember any light that comes on in your car go have it check out and do the work yourself. saving you lots of cash.
nick