Confirming a report in news weekly Der Spiegel, Germany's transport ministry told AFP it was investigating the use of a new “illegal defeat device” in some 60,000 Audi cars, half of which are driving on German roads.
According to Spiegel, the current A6 model is equipped with software that deliberately slows down the use of a special pollution-cleaning fluid in the final 2,400 kilometres of its life span, to avoid drivers having to refill the so-called AdBlue liquid in between regular service updates.
But reducing the AdBlue function also drastically lowers its effectiveness in neutralizing the engine's harmful nitrogen oxides, making the diesel cars far more polluting during that time.
“An official recall for at least the affected Audi cars registered on German roads is highly likely,” Spiegel wrote, without citing its sources.
“Production of the model has been halted in the meantime,” it added.
Germany's transport ministry said its KBA vehicles licensing had opened a probe into suspicions that Audi equipped some 60,000 “A6/A7 models” with a cheating device, “around 33,000 of them in Germany”.
Audi said it would release a statement on the matter later on Tuesday.
It's not the first time the German car industry has been accused of AdBlue tampering, with Daimler and Volkswagen both facing the threat of mass recalls over similar accusations in February.
The alleged AdBlue scam differs from the one that sparked Volkswagen's “dieselgate” crisis in 2015, when the auto giant admitted to installing software in some 11 million diesels worldwide that could detect when a vehicle was undergoing pollution tests and reduce emissions accordingly.
Outside the lab however, the cars were vastly more polluting, spewing up to 40 times more toxic gases than legally allowed.
The scandal, which affected VW's own brand cars but also those made by Audi, Porsche, Skoda and Seat, has so far cost the group more than €25 billion in buybacks, fines and compensation, and it remains mired in legal woes at home and abroad.