Oliver Schmidt is a former manager of a VW engineering office in suburban Detroit. He was arrested in January while on vacation in Miami.
VW admits using software to get around emission standards. It pleaded guilty in March to defrauding the U.S. government and agreed to pay USD 4.3 billion in penalties, on top of billions more to buy back cars.
Schmidt is accused of telling regulators technical problems were to blame for the difference in emissions in road and lab tests. He could face up to seven years in prison when he is sentenced on Dec. 6.
The software detected when cars were being tested and turned the emission controls off during normal driving. The result was the cars emitted more than 40 times the U.S. Limit for the pollutant nitrogen oxide.
Some 11 million cars worldwide were equipped with the software.