Every car built since 1996 has a diagnostic computer connection under the dash called an OBD-II which allows mechanics to plug in and find out what that annoying red light on the dash is trying to tell you. Of course, getting a mechanic to plug in and tell you what’s wrong will probably cost you at least $100.
Luckily for us all, there is now a service called CarMD.com which allows anyone to plug into their car and then check the Web to find out what the issue is on their own.
A $90 tool is required which is what actually interfaces with your cars OBD-II port, and after you’ve read the code from the car you plug it into your computer to get an explanation of what the trouble code really means.
Obviously this tool could save it’s own cost during it’s first use by simply understanding what the problem is. It might be something simple enough that you can fix it yourself, or it might save you a bundle by being able to let the mechanic know that you are aware that the problem is, for example, just an oxygen sensor as opposed to needing an engine overhaul.