A U.S. regulator found software in some Audi vehicles that lowered their carbon dioxide emissions if it detected they were being used under test conditions, Bild am Sonntag reported.
The California Air Resources Board (CARB) discovered the software in an automatic transmission Audi last summer, the German weekly newspaper said, without citing any sources.
CARB and Audi declined to comment on Sunday's Bild am Sonntag report.
The paper said the device, which was not the same as the one which triggered last year's diesel emissions scandal at Audi parent Volkswagen, was also used in diesel and gasoline-powered cars in Europe.
VW's admission that it had installed software that deactivated pollution controls on more than 11 million diesel vehicles sold worldwide, triggered the deepest business crisis in the German carmaker's history.
Audi, the main contributor to VW group profit, has also admitted its 3.0 litre V6 diesel engine was fitted with emissions-control software.
Bild am Sonntag said the software discovered by CARB, which was installed in vehicles with certain automatic transmissions, detected whether a car's steering wheel was turned.
If it was not, indicating laboratory testing conditions, the software turned on a gear-shifting program which produced less carbon dioxide than in normal road driving. If the wheel was turned in any direction by more than 15 degrees, the program was switched off, the paper said.
Audi stopped using the software in May 2016, just before CARB discovered the manipulation in an older model, the paper said, adding that the carmaker had suspended several engineers in connection with the matter.
Bild am Sonntag said a spokesman for Audi had declined to comment, citing ongoing talks with U.S. and California regulators on a proposed fix for cars with 3.0 litre engines.