ACDelco GM Original Equipment Flex Fuel Sensors monitor the ethanol content of the fuel in your flex fuel vehicle, and are GM-recommended replacements for your vehicle's original components. The flex fuel sensor signal is used by the engine control module to adjust the air/fuel mixture and ignition timing for efficient operation. These original equipment flex fuel sensors have been manufactured to fit your GM vehicle, providing the same performance, durability, and service life you expect from General Motors.