ACDelco GM Original Equipment Engine Variable Valve Timing Solenoids regulate oil flow to the cam phasers that change the timing of the camshafts. The desired positions of the camshaft varies with engine speed and load and is calibrated for optimal engine performance, drive quality, and fuel economy. They are GM-recommended replacements for your vehicle's original components. These original equipment solenoids have been manufactured to fit your GM vehicle, providing the same performance, durability, and service life you expect from General Motors.