ACDelco GM Original Equipment Engine Camshaft Position Sensors monitor the rotational position of the camshaft(s), and are GM-recommended replacements for your vehicle's original components. They provide a signal to the engine control module which compares the camshaft position with the crankshaft position to determine ignition and fuel injection timing. These original equipment engine camshaft position sensors have been manufactured to fit your GM vehicle, providing the same performance, durability, and service life you expect from General Motors.