Hopefully you will find an OBD code causing the problem. I am not sure about your vehicle, but on some you can turn the key on, off, on 3 times, and a code will pop up on the digital dash.
You should be able find out if you can do this on your vehicle looking on the net.
If not, stop in at an Auto Zone and have them check your OBD codes. Free check. If there is a code they can tell you which part needs replaced.
Good luck.