Illegal methods in motor vehicles to overcome emissions controls
Evaluation and Development control room in the EPA's Motor Vehicle Test Center in Ann Arbor, Michigan, 1973
A defeat device is any motor vehicle hardware, software, or design that interferes with or disables emissions controls under real-world driving conditions, even if the vehicle passes formal emissions testing.[1][2] The term appears in the US Clean Air Act and European Union regulations, to describe anything that prevents an emissions control system from working, and applies as well to power plants or other air pollution sources, as to automobiles.[1][2][3]
The United States Environmental Protection Agency (EPA) has taken numerous enforcement actions against car makers and other companies that have used or installed defeat devices, whether deliberately, or through error or negligence. Aftermarket parts or software, such as modified exhausts or chip tuning products and services, are considered defeat devices if they inhibit or bypass a vehicle's emissions controls.[3]
FAQ – Air pollutant emissions standardsArchived 2015-10-13 at the Wayback MachineEuropean Commission, 25 September 2015. Quote: Article 5 (2) of Euro 6 Regulation 715/2007/EC prohibits the use of defeat devices. Article 3(10) defines defeat device as any element of design which senses temperature, vehicle speed, engine speed (RPM), transmission gear, manifold vacuum or any other parameter for the purpose of activating, modulating, delaying or deactivating the operation of any part of the emission control system, that reduces the effectiveness of the emission control system under conditions which may reasonably be expected to be encountered in normal vehicle operation and use.