ACDelco GM Original Equipment Ignition Knock (Detonation) Sensors monitor the engine for pinging or spark knock, and are GM-recommended replacements for your vehicle's original components. These sensors create a voltage signal based on the vibrations caused by erratic air/fuel mixture combustion; the engine control module uses these signals to adjust the ignition timing and air/fuel mixture. These original equipment ignition knock sensors have been manufactured to fit your GM vehicle, providing the same performance, durability, and service life you expect from General Motors.