Okay, first: Steph V - this is the grand AM forum, you might have better luck in the grand PRIX forum.
That being said, the grand ams are known to have bad front wheel hubs, of which the traction control/ABS sensors are a part of. Not sure if this applies to the grand prix. This causes the problems described. In addition, the traction control will shut itself off when the car is started.
If and when you do get these replaced, go for the aftermarket replacement, not the factory GM part, as they are much stronger and better built parts. I went through 3 GM parts, each replaced after only 6 mounths, before going aftermarket. The new one has lasted 22 mounths now. Don't let the cost differance deter you, you get what you pay for.