Porsche Cayenne Diesel
Porsche's Cayenne diesel model as shown in their website.Porsche

Volkswagen has found itself embroiled in a widening emissions scandal after the US Environmental Protection Agency accused the company of using illegal software in certain six-cylinder diesel engines that drags Porsche and luxury Audi and VW models into the net. The EPA claims in a notice that the automaker developed and installed software that masks emissions in VW, Audi and Porsche vehicles equipped with 3.0 litre V6 diesel engines for model years 2014 through 2016.

The new list now covers the 2015 Porsche Cayenne, the 2014 VW Touareg, , and the 2016 Audi A6 Quattro, A7 Quattro, A8, A8L and Q5. The notice covers about 10,000 diesel passenger cars sold in the US since the model year 2014. The number of cars affected for 2016 cars has not yet been established, the EPA said.

The inclusion of Porsche in its latest allegation puts newly appointed VW chief executive Matthias Mueller in a tricky position. He led Porsche prior to taking over his latest position at the VW Group. And given that the model year was 2015, it goes without saying that if found to be true, the emissions scandal could have happened during his leadership at Porsche.

This is the second notice of violation issued by the EPA. Its initial findings were released on 18 September in which the EPA accused VW of using illegal software on certain 2.0 litre engines for model years 2009 to 2015 vehicles which cover the Jetta, Jetta Sportwagen, Beetle, Audi A3, Golf, Golf Sportwagen and Passat.

The EPA, in a statement, said that the latest models found to be in violation of its emissions laws, senses that it is undergoing an emissions test procedure and operates in a low NOx temperature conditioning mode which meets emissions standards. "At exactly one second after the completion of the initial phases of the standard test procedure, the vehicle immediately changes a number of operating parameters that increase NOx emissions and indicates in the software that it is transitioning to "normal mode" where emissions of NOx increase up to nine times the EPA standard, depending on the vehicle and type of driving conditions."

VW and Porsche deny fresh allegations

In a statement, VW Group confirmed that it had been informed by the EPA on Monday (2 November) that its vehicles with V6 TDI engines "had a software function which had not been adequately described in the application process." The company said it wished to stress that "no software had been installed in the 3-litre V6 diesel power units to alter emissions characteristics in a forbidden manner."

Reuters noted that VW made similar denials for more than a year to the same US regulators before finally admitting to cheating on the 4-cylinder diesels. In September, the company said it had installed the cheat software in its 4-cylinder engines on about 482,000 cars in the US and more than 11 million worldwide. It is in the process of recalling the affected vehicles to fix the problem.

A VW Group source told the news agency: "We want to know more from the regulators about how they came to this conclusion. We're not sure how they came up with their findings, and would like a better opportunity to review the data with the regulators." The V6 diesel engine designed by VW's Audi unit is widely used in the group's premium models in model years 2014 through 2016.

In a separate statement, Porsche Cars North America said: "We are surprised to learn this information. Until this [EPA] notice, all of our information was that the Porsche Cayenne Diesel is fully compliant." The company said it will cooperate fully with all the relevant authorities.

EPA warns more vehicles' emissions testing ahead

The EPA claims in its second notice that the vehicles had one or more Auxiliary Emission Control Devices that the company failed to "disclose, describe and justify" in their applications for certificate of conformity for each model. Manufacturers need to apply for a certificate of conformity for each model and for each year before they can introduce the cars into the market. "An AECD designed to circumvent emissions test is a defeat device," it added.

It said that following the first notice, the EPA had updated its testing procedures "specifically designed to detect potential defeat devices" and it is under the new testing regime that further violations were uncovered. The tests were conducted by three regulators: the EPA's National Vehicle and Fuel Emissions Laboratory, California Air Resources Board's Haagen-Smit Laboratory and Environment Canada's River Road Laboratory.

The regulator warned VW that it may be liable for further civil penalties and injunctive relief and ordered VW to "address these issues. It is Volkswagen's responsibility to fix the vehicles' emissions systems."

It continued: "This is a very serious public health matter. ARB and EPA will continue to conduct a rigorous investigation that includes testing more vehicles until all the facts are out in the open. The EPA added: "VW will have an opportunity to respond to the allegation contained in the NOV."

How did the cheating go undetected for so long?

Fred Upton, the House Energy and Commerce Committee chairman said in a statement: "The latest revelations raise the question, where does VW's road of deceit end? he said the latest notice "prompts questions regarding the prevalence of the emissions cheating and how it went undetected for so long."

Two Democrat Senators, Richard Blumenthal and Edward Markey also had strong words for VW. They said the automaker "should be held accountable for illegally using defeat devices to cheat consumers and emissions controls. The administration should reverse any CAFE or other benefits VW might have enjoyed as a result of illegal behaviour." CAFE is the Corporate Average Fuel Economy aimed at improving the average fuel economy of cars, trucks, vans and sport utility vehicles produced for sale in the US.