On Friday, the US Environmental Protection Agency (EPA) accused Volkswagen Group of purposely installing software on some of its cars to cheat on emissions tests. According to the New York Times, Volkswagen Group will have to recall 500,000 Volkswagens and Audis on which so-called defeat devices were installed.
In a Notice of Violation (PDF) sent to the automaker, the EPA said that the defeat devices on Volkswagen Group's cars render inoperative elements of the vehicle's emission control system. If the car senses that it's operating normally, the defeat device reduces the effectiveness of some or all of the car's emission control components. However, if the car is undergoing an emission test, the emission control systems will be allowed to function normally.
According to the EPA's letter, the software on Volkswagens and Audis was installed on the cars' electronic control module and determined whether the car was driving normally or undergoing testing based on various inputs including the position of the steering wheel, vehicle speed, the duration of the engine's operation, and barometric pressure. If the car was driving under normal conditions, the car's nitrogen oxide (NOx) emissions were increased by 10 to 40 times above the level of NOx emissions permitted by the EPA.