This looks nasty...and they got caught...

"The Environmental Protection Agency on Friday accused Volkswagen of installing software on 482,000 diesel cars in the U.S. to evade federal emission regulations, potentially exposing people to harmful pollutants.The German automaker adopted what the EPA called a "defeat device" to trick U.S. regulators into believing that its cars met Clean Air Act standards, the federal agency said in a statement.
The agency said the diesel cars that violated federal standard were the 2009-14 Volkswagen Jetta, Beetle and Golf, the 2014-15 Volkswagen Passat, and the 2009-15 Audi A3.
Those cars emitted nitrogen oxides, which can exacerbate respiratory conditions such as asthma, at up to 40 times the standard level, the EPA said.
Volkswagen admitted to investigators that it had installed the defeat device, the EPA said." ...(more)

EPA accuses Volkswagen, Audi of evading emission laws