I have an across this issue a few times, two times it was the lock cylinder and three times it was a low voltage condition caused by a faulty BCM (body control module). The most important thing you can do right now is make sure that your battery is fully charged and has at least 12.6 volts, or you could try hooking up a jump box to it and see if that helps. If the battery has good voltage. Tthen it requires some pretty extensive testing and equipment to determine whether it is the lock cylinder or BCM. But make sure of the battery condition before you go any further.
If everything checks out here is the ignition switch replacement diagrams below.
Check out the diagrams (below). Please let us know if you need anything else to get the problem fixed.
Images (Click to enlarge)
Saturday, February 15th, 2014 AT 7:01 PM