Last month, Volkswagen apparently admitted that it had used "defeat device" software to evade emission controls in 482,000 cars sold in the U.S. with three versions of its 2.0-liter TDI diesel engine.

Then, yesterday, the EPA issued a complaint in which it accused VW of incorporating similar software into its 3.0-liter V-6 diesels, which are used by Audi and Porsche as well.

This time, the response was from the headquarters of Volkswagen AG in Germany--which came out swinging.

DON'T MISS: VW Diesel V-6 Engines Used By Audi, Porsche Have Cheat Software Too: EPA

The U.S. units of both Volkswagen and Audi referred all questions to the statement from the German parent group, which denied that any emission-related software installed in those engines had been used "in a forbidden manner."

That's slightly different than saying that the EPA's claims weren't accurate. The full EPA "Notice of Violation" can be read here.

The full statement from Volkswagen AG reads as follows:

2014 Audi A7 TDI

2014 Audi A7 TDI

The United States Environmental Protection Agency (EPA) informed Volkswagen Aktiengesellschaft on Monday that vehicles with V6 TDI engines had a software function which had not been adequately described in the application process.

Volkswagen AG wishes to emphasize that no software has been installed in the 3-liter V6 diesel power units to alter emissions characteristics in a forbidden manner.

Volkswagen will cooperate fully with the EPA clarify this matter in its entirety.

ALSO SEE: VW Diesel Owners In Limbo Until Recall Issued, While Cars Lose Value

UPDATE: Late in the day on Tuesday, November 3,Porsche's U.S. arm issued a second statement, as follows:

Porsche Cars North America, Inc. today decided, in view of the unexpected U.S. EPA notice received yesterday, to voluntarily discontinue sales of model year 2014 through 2016 Porsche Cayenne Diesel vehicles until further notice.

We are working intensively to resolve this matter as soon as possible. Customers may continue to operate their vehicles normally.

The U.S. arm of Porsche, meanwhile, issued its own statement yesterday afternoon, before the VW Group response was sent out.

The Porsche statement says:

Late this morning, Porsche Cars North America, Inc. received a notice of violation from the United States Environmental Protection Agency (EPA) regarding the 2015 Porsche Cayenne Diesel.

2013 Porsche Cayenne Diesel

2013 Porsche Cayenne Diesel

We are surprised to learn this information. Until this notice, all of our information was that the Porsche Cayenne Diesel is fully compliant.

Porsche Cars North America will cooperate fully with all relevant authorities.

About 10,000 sedans, hatchbacks, and SUVs from the three makes are named in the EPA complaint.

FOR MORE: VW Diesel Emissions Recall: What You Need To Know In 10 Questions:

Vehicles affected include the 2014 Volkswagen TouaregTDI and the 2015 Porsche Cayenne Diesel.

Audi has the most models in the complaint, with five 2016 models named: the A6, A8, and A8L TDI sedans; the A7 TDI hatchback; and the Q5 TDI sport-utility vehicle.

According to The Detroit News, the U.S. arm of Audi said it will not immediately issue a stop-sale order for its V-6 TDI models.

2014 Audi Q5 TDI, Catskill Mountains, Oct 2013

2014 Audi Q5 TDI, Catskill Mountains, Oct 2013

[UPDATE: "A stop-sale [has] not been issued, we are working with the EPA to understand the tests that they conducted," wrote Audi of America senior communications manager Mark Dahncke to Green Car Reports. "There is no so-called defeat device on the 3.0 diesel engines."]

While the four-cylinder TDI diesels cited in the EPA's September complaint were priced from $20,000 to perhaps $40,000, the newly-named cars with the V-6 diesel engines run from perhaps $40,000 to as high as $100,000, depending on trim levels and options.

As news and additional information becomes available, Green Car Reports will update this story.


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