Check engine

Okay guys, my sister has a '97 Eclipse GS automatic and her check engine sign came on and I have no idea what it is. The first time it came on we replaced the spark plugs and the light went away. About a month or so later, the light came on again and this time, we changed the chord (or coils or whatever they're called) that was connected to the spark plugs and the light went away again. And now, about a month later, it's back again. Does anyone know what it could be? Ugh, this is frustrating!

Goto autozone and have them pull the codes for free

What does pulling the codes mean?

means hooking up a diagnostics system to your ecu, the diagnosis system will give you error codes. Then check what your error codes means and thats your problem