Ok, so basically I didn't get an answer that I was looking for so with this wonderful world of information on the net I actually did some really good searching and found this:

The TCM has a safe mode that it goes in to when it detects a fault in the system. This mode is referred to as "Limp In". Basically, anytime there is a transmission related fault code the computer commands the computer to stay in second gear only. The gearing for second is such that it will allow the driver to accelerate from a stop without bogging out as well as maintain speeds up to around 45 mph. This enables the driver to drive the car until out of harms way as well as possible make it to a repair shop. In order to remove the TCM from "Limp In", the dtcs have to be erased. This can be done by removing the fuse labeled "Engine" in the power distribution center (PDC) which is the fuse and relay block next to the battery. Otherwise, the DTC's have to be removed with the use of a scan tool. Some generic scan tools are not capable of reading any TCM information or TCM specific codes. If there are any TCM DTCs, the PCM will have code P0700 TCM DTCs Present.

I suspect that my problem might not be internal, but I'll have to take it to the dealership just to make sure. God, I hope it's one of these sensors.