Due to the many reasons the Service Engine Soon light would come on, I usually recomend checking the gas cap (sometimes the light will come on if the cap is loose or missing), and if that's good, get the light checked by a local auto parts store that offers free code reading. Most national chain auto parts stores like Autozone and Advance Auto Parts, and many local parts stores are catching on. So get the code read, and if you need more help, please let me know (along with the code).