If you mean the "CHECK ENGINE" light, that means a code has been generated by the ECM.

Take the car to Autozone and they will read it for you, then report back here with the code and we can go from there.
OR you can get an Ultragauge for about $75 and read the code yourself - mine stays in the car on the dash all the time, I use it to monitor several parameters on an on-going basis.