There is an expensive tool that you can plug in to your car that will tell you why your throwing the CEL, which is kind of important if your going to try to make it go away
Go to your local Auto zone or whatever lots of places will pull the code for free!
The Ultimate CEL Thread!
^Linky-Clicky^ to find out what your problem is then you can fix the problem knowing for sure what is causing it

 

I got a check engine light when I cut out my stock resonator. It comes on and off occasionally. Its the same code everytime - I think the reduced pressure made the ECU think there was a leak or that my cat was going.