If you take it to autozone I think they will scan the codes for free, this code will give you an idea of where to start trouble shooting. In other words it will tell you what system is malfunctioning. If your autozone employees are anything like the ones around here then don't listen to thme because they are a bunch of fucking retards who thing what ever the code says is what is broken. For example I had a friend who had a tps code in his car, they told him he needed a tps sensor, so he bought one. Still had the code so they told him his ecu must be bad :noo so he bought one, still had the code. Finaly the dumbs ass calls me (most people will call there friends that are mechanics before throwing parts at a car, but not him :bash) I told him I would look at it when I got home. He had a ground wire that had broke in half. He spent over $200 when all he needed was about .002 cents worth of soilder.
So anyways what I'm tring to say is ask us when you find out what trouble code you have.