VW is in hot water. The company needs to recall 500,000 vehicles because it supposedly bypassed emissions test using software called 'defeat device' which bypasses emissions tests. If proven guilty, VW could face massive fines.
Involved in this recall are the 2009-2015 Volkswagen Golf, Jetta and Beetle, the 2014-2015 Volkswagen Passat and the 2009-2015 Audi A3. The 'defeat device' detects when the car is undergoing emissions testing and turn on all of the car's emissions control systems then. In normal driving, the systems would turn off, causing 40 times larger nitrogen oxide emissions, according to the E.P.A.
Why did VW resort to this, likely to increase performance and fuel efficiency since emissions control do make performance more sluggish. The recall is in effect in the US.