MKW:
CGX car nut:

Volkswagen is denying the EPA's allegations with any software modifications to the auxiliary emission control devices as defined in the EPA's Notice of Violation letter for the 3.0 l  I  engines, issued earlier today.  What is interesting is that the Volkswagen Group has had several of the vehicles on sale for more than a couple of years than what is defined in the EPA classification of the violation group.  

VW's carefully worded response seems ,to me , like it will just dig itself a deeper hole . In one news story, they deny vehicles have software designed to cheat tests. Instead the company says that ( US 2014-16 ) cars with the 3.0 litre diesel V6 engines "had a software function which had not been adequately described in the application process". 

One must remember that there are numerous "secret" negotiations between the EPA and industry on a variety of issues and regulations.  The EPA issues a number of exemptions to various automakers; however, the authority fully resides with the EPA, usually through California's CARB, to certify models as being in compliance with standards.  This appears more as a negotiation strategy, at this juncture, to pressure Volkswagen, for some reason.  

Here is an article on the subject in The Wall Street Journal: http://www.wsj.com/articles/epa-notifies-volkswagen-of-added-emissions-violations-1446491504