This really sounds like a wiring issue or circuit issue to me. The wheel speed sensors probably aren't the culprit, nor the wiring to them, or you'd be getting messages for ABS and TCS systems as well.
The GP's don't have a reset button in the side fuse box like the Regal's, I looked to make sure, but the only way to reset the tire pressure system is through the DIC.
If I were you, I'd first just try unhooking the battery for a while. It may just be a glitch if you're lucky. If that doesn't work, Morad Parts has 5 button DIC's every once in a while, I'd just check him or eBay itself for one at a good price. If the battery doesn't fix it, there's either a short in the wiring or the DIC itself has a hard fault in the circuit board. If you're in the mood, you can open it up and look for anything burnt, or see if it smells burnt. Burnt circuits have a special smell to them...
