Originally Posted by Woodrow

Well nothing is free unless you take it to autozone and have them do it. However, there is no guarantee that scanning it will yield results unless there is a DTC. 99% of the time their little codereader will only read codes and the rest is up to you.
Usually if you want a technician to diagnose/scan expect to pay anywhere from 1/2 to 1 hours worth of labor of that shop. A technician's time is money.