The Pontiac Grand Prix uses a serpentine belt to drive the various accessories mounted to the engine block. This serpentine belt is made of rubber, and over time, it can stretch, fray, tear or even break. When the belt does break, all accessories will cease working, and you'll have difficult driving the vehicle if it's even drivable at all. Preventive maintenance is the key here, and you should remove and replace the belt when it first shows sign of wear.
Locate the belt routing diagram located on a sticker on the underside of the hood. Make sure you find this sticker prior to disassembling the belt, so you know how to properly run the replacement belt around the pulleys.
Locate the tensioner on the front of the engine block. It's on the passenger side of the engine block, just to the left of the crankshaft pulley. Turn the tensioner clockwise using the 3/8-inch breaker bar and sockets. Pull the belt off the pulleys with the tensioner held in place.
Route the replacement belt around the pulleys on the engine following the diagram you found in step 1, making sure to keep the belt flat and straight in each pulley, and make sure it doesn't twist in the process.
Turn the tensioner clockwise again, then route the belt around the tensioner. Release the breaker bar again so that the tensioner contacts the belt.
