Volkswagen has disclosed to U.S. regulators that there is additional suspect software in its 2016 diesel vehicles that would potentially help their exhaust systems run cleaner during government tests.

Volkswagen confirmed to The Associated Press that the “auxiliary emissions control device” at issue operates differently from the “defeat” device software included in the company’s 2009 to 2015 models disclosed last month. That disclosure triggered the worldwide cheating scandal engulfing the world’s largest automaker.

The newly revealed software makes a pollution control catalyst heat up faster, improving performance of the device that separates smog-causing nitrogen oxide into harmless nitrogen and oxygen gases.

Volkswagen spokeswoman Jeannine Ginivan said the new issue with the 2016 diesel models, known as an auxiliary emissions control device, was first revealed last week to U.S. Environmental Protection Agency and California regulators.

“This has the function of a warmup strategy which is subject to approval by the agencies,” Ginivan said. “The agencies are currently evaluating this and Volkswagen is submitting additional information.”