The camshaft position sensor on a Pontiac Grand Prix is a digital sensor that creates an on and off pulse that tells the engine computer where the valve train is positioned relative to the crankshaft of the engine. The computer decides when the fuel injectors should fire based on this information.
A magnet is mounted on the outer part of a ring attached to the engine camshaft. The camshaft position sensor is near that ring. As the magnet approaches the sensor in its rotation, it produces electric current, or a pulse. The speed and timing of these pulses determines valve train position and speed.
The camshaft position sensor mounts on the front of the engine, just above the crankshaft pulley. It is also to the left lower side of the serpentine belt idler pulley. The sensor typically has two wires leading from it.
The camshaft position sensor is held in by one bolt. Remove that bolt, and disconnect the electrical plug to remove the sensor from the engine.
