Federal regulators fired off a new round of accusations at Volkswagen on Monday, alleging that it also installed secret software on some Audis and Porsches to hoodwink emissions tests.
VW admitted in September that it rigged U.S. emissions tests by installing the software in some 2009-15 model-year vehicles with 2-liter diesel engines. The new charges, which the Environmental Protection Agency and the California Air Resources Board detailed in a six-page notice of violation to the company (PDF), drags VW's ritzy Porsche line into the scandal for the first time.
The notice targets about 10,000 3-liter diesel versions of the 2014 VW Touareg, the 2015 Porsche Cayenne and the 2016 Audi A6 Quattro, A7 Quattro, A8, A8L and Q5.
Certain models of the Audi A3 were already subject to the recall.
Including the earlier round of accusations, VW now faces recalls of 11 million cars around the world. The German company has set aside more than $7.2 billion to cover the expected cost of resolving the scandal.
"VW has once again failed its obligation to comply with the law that protects clean air for all Americans, said Cynthia Giles, the EPA's assistant administrator for compliance. "All companies should be playing by the same rules."
VW denied the new allegations, saying no such software had ever been installed in the 3-liter vehicles and promising to cooperate with the EPA to get to the bottom of things.
The EPA notice says the cheating module senses when the car is being tested and chokes off emissions of nitrogen oxide, which reacts in the air to form corrosive nitric acid and poisonous organic nitrates.
Exactly one second after the test is completed, the module revs up several parts of the engine, sending nitrogen oxide spewing out in volumes as much as nine times what the test would have recorded, the agency said.
The California Air Resources Board said it was "very disappointed with this development" and set a Nov. 20 deadline for VW to draft a recall plan.
"This is a very serious public health matter," said Richard Corey, the board's executive officer.