Reprinted from: http://www.freeautomechanic.com/checkenginelight.html

The first thing to do when your "Check Engine Soon" light comes on is to determine the immediate cause. Consider if the vehicle is still performing as usual or if a loss of performance is noticeable. Generally a constant illuminated light without loss of performance points to an emissions related issue( this won't leave you stranded). When the light flashes, this indicates a serious engine failure condition and will require immediate attention. You may wish to take your vehicle to a local shop and have Computer Diagnostics performed. Usually costs under $100.00.

Generally all vehicles from 1996 and up have an OBD II computer. The Major problem when it comes to OBD II is that you can no longer acquire the trouble codes by counting the flashes of the Check Engine light like you could on earlier OBD I vehicles. You can take your car into a local high-tech service shop, where the minimum charge for computer diagnostics and engine diagnostics might cost you somewhere into three digits. Or you may want to learn about OBD II systems. in order to do so you will need an OBD II scan tool. I have already done the research for you and located several different scan tools for you to choose from. If you already have the code and need to know what it means check out our complete list of OBD II Codes Here.