At the beginning of November, the United States' Environmental Protection Agency (EPA) issued a second notice of violation against the Volkswagen Group, claiming that certain cars powered by the company’s 3.0-litre turbo-diesel V6 engines were fitted with a defeat device, which allowed it to illegally pass American emissions testing for NOx (oxides of nitrogen).
The EPA alleged that the engine’s control software was able to detect an emissions test and enter a “temperature conditioning” mode that limited the output of NOx. When the test is concluded, the engine reverts to operating in its regular configuration, emitting up to nine times the permitted levels of NOx.
According to a statement just released by Audi's American arm, latest violation notice relates to "AECDs (Auxiliary Emission Control Devices) [which] were not sufficiently described and declared in the application for US type approval".
The company has confirmed that three AECDs were not fully declared to the EPA. One AECD is responsible for "temperature conditioning of the exhaust‑gas cleaning system", another is designed to avoid "deposits on the Ad-Blue metering valve", while the last one prevents "[hydrocarbon] poisioning of the SCR catalyst".
Audi claims that the temperature conditioning AECD is "regarded as a defeat device according to applicable US law".
The luxury brand is currently working on updating its documentation and software for the cited devices. It has "agreed with the environmental authorities on further steps of cooperation in which the concrete measures to be taken will be specified". Audi has "committed to continue cooperating transparently and fully", and the focus is now on "finding quick, uncomplicated and customer-friendly solutions".
Audi was responsible for the development of this engine, which has been used in the A6, A7, A8, Q5 and Q7 models sold Stateside since the 2009 model year. The 3.0-litre V6 TDI has also been used in the Volkswagen Touareg and Porsche Cayenne since the 2013 model year. Note that model years in the US can start up to 12 months ahead of the calendar year.
Since the EPA formally handed in latest notice of violation, the three brands have withdrawn cars with the suspect V6 TDI engine from sale in the USA. This stop sale measure has been "extended until further notice".
There are an estimated 85,000 Volkswagen, Audi and Porsche models sold in the US since 2008 with the affected 3.0-litre V6 TDI.
More: All the news related to the Volkswagen Group's "dieselgate" affair.