It appears that the Volkswagen Group’s dieselgate woes continue to deepen. This is because the United States Environmental Protection Agency (EPA) has recently issued a second notice of violation (NOV) of the country’s Clean Air Act (CAA) to five companies under the Volkswagen Group banner.

Volkswagen AG, Volkswagen Group of America, Porsche AG, Porsche Cars North America, and Audi AG, have all been issued the NOV, which closely follows the same premise as the previous one issued back in September, alleging that Volkswagen developed and installed a defeat device on its diesel vehicles.

This time, it involves the Group’s 3.0 litre TDI V6 engine found in Volkswagen, Audi, and Porsche passenger vehicles for model years (MY) 2014 through 2016. As a short recap, the defeat devices (software in the electronic control module) enables the vehicle to sense when it is being tested for compliance with EPA emissions standards.

During that time, the vehicle engages measures to ensure that it meets the EPA’s emissions standards. However, once the test procedure is concluded, the vehicle will reconfigure itself back to a “normal” setting where nitrogen oxides (NOx) increase. In this instance, the 3.0 litre diesel engine is said to increase emissions of nitrogen oxide (NOx) up to nine times of the EPA’s standard.

The models affected are all sold in the US, and it is yet unknown if other markets will be involved as well. In the EPA’s NOV, it listed several SUV and sedan models including the 2014 Volkswagen Touareg, 2015 Porsche Cayenne, as well as the model year 2016 Audi A6 quattro, A7 quattro, A8, A8L, and Q5.

Both the EPA and the California Air Resources Board (CARB) have started investigations based on Volkswagen’s alleged actions. The NOV covers roughly 10,000 diesel passenger cars already sold in the US since model year 2014. However, the number of 2016 vehicles covered by the NOV has yet to be known.

Volkswagen has already responded to this latest allegation by emphasising that “no software has been installed in the 3.0 litre V6 diesel power units to alter emissions characteristics in a forbidden manner.” Volkswagen also stated that it will cooperate fully with the EPA to clarify this matter in its entirety.