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Audi expects it will cost 10s of millions of euros to bring engines in line with US law (Photo: Audi)

Audi admitted that so-called defeat devices are present in the US versions of its V6 TDI 3-liter diesel powertrains and promised to update software to bring the engines into compliance.

The German premium car brand, which is part of the Volkswagen Group, was responding to a notice of violation (NOV) issued by the US Environmental Protection Agency on Nov. 2. This NOV said VW had developed and installed defeat devices in certain VW, Audi and Porsche cars equipped with 3.0 liter engines for model years 2014 through 2016.

Audi confirmed Monday that the three brands were affected and that it would cost "in the mid-double-digit millions of euros" to provide a remedy that would be approved by US authorities.

The carmaker said three "auxiliary emission control devices" it had installed were not declared in line with US approvals. One of the devices takes care of temperature conditioning of the exhaust-cleaning system, while the other two help avoid deposits resulting from the emissions cleaning process. The device used for temperature conditioning "is regarded as a defeat device according to applicable US law," Audi said in a press release.

In September, Volkswagen admitted installing defeat devices on a wide range of US models equipped with smaller diesel engines. The devices helped it meet stringent emission tests in the US. In the wake of the revelations, Europe's largest carmaker had to swap out much of its top management. It also faces billions of euros in legal and recall costs.