The United States Environmental Protection Authority (EPA) has hit the German brands with an official notice of violation, stating that "four-cylinder Volkswagen and Audi diesel cars from model years 2009-2015 include software that circumvents EPA emissions standards for certain air pollutants".
Volkswagen is also under investigation by California Air Resources Board (CARB). After being presented with evidence of its wrongdoing, "Volkswagen admitted that the cars contained defeat devices".
Affected four-cylinder diesel cars from Volkswagen and Audi are fitted with a "sophisticated software algorithm", which detects when the vehicle is undergoing official emissions testing, turns on all of the car's emission control systems and allows it to pass the test.
Under normal driving, though, the cars emit up to 40 times the amount of permitted oxides of nitrogen (NOx). NOx pollution adds to ground-level ozone and increases particulate matter in the atmosphere. These pollutants can lead to respiratory problems and impact on the health of children and the elderly, and result in asthma attacks, hospitalisation and premature death.
Vehicles fitted with the evasive software include the diesel versions of the Volkswagen Beetle, Golf, Jetta, and Passat, as well as the Audi A3. All up 482,000 diesel-powered Audis and Volkswagen are said to have the defeat mechanism installed.
This violation of the federal Clean Air Act was discovered by researchers at West Virginia University and the International Council on Clean Transportation.
According to the EPA, "it is incumbent upon Volkswagen to initiate the process that will fix the cars’ emissions systems", although owners of the affected vehicles are free to continue driving and reselling their vehicles as they see fit.