^^ This, check the plug going into the output of your transmission.. there's a sensor with a 2 wire plug going into it. I bet the belt or something jerked that wiring or hit the sensor causing a short or something...

See sensor #10 in the pic below... the wiring harness drops down behind the alternator IIRC. While you are under there check to make sure it did not unhook anything else.

http://www.justanswer.com/pontiac/3k...rand-prix.html