WASHINGTON- Volkswagen is accused of cheating on a second set of emissions tests, this one involving six-cylinder diesel engines.

The EPA says the automaker installed software designed to defeat emission on the 2014 to 2016 models. It previously admitted rigging emissions testing for four-cylinder diesel engines. EPA says the software has a timer that makes the cars perform differently when being tested then they perform on the road.

The agency charges the engines give off up to 9 times more nitrogen oxide pollution while being driven than they do when they're being tested.

The violations encompass 10,000 vehicles. They include the 2014 Tourareg, 2015 Porsche Cayenne and the 2016 Audi A6 Quattro, A7 Quattro, A8 and Q5.