Under a revision of the charges, he pleaded guilty to two counts: conspiracy to defraud the federal government and violating the Clean Air Act. A third charge of aiding and abetting wire fraud was rolled into the conspiracy charge.

Mr. Schmidt admitted conspiring with other Volkswagen employees to mislead and defraud the United States in 2015 by failing to disclose that thousands of diesel cars were rigged to evade detection of excess emissions levels. He also admitted filing fraudulent emissions reports to regulators.

Mr. Schmidt faces maximum penalties of five years in prison and a $250,000 fine on the conspiracy charge, and two years in prison and a $250,000 fine on the environmental charge. He is to be sentenced on Dec. 6.

There was no discussion at the hearing of his potential role as a witness in other federal cases.

Volkswagen has already pleaded guilty to charges of conspiracy to commit wire fraud and to violate the Clean Air Act, customs violations and obstruction of justice.

The company agreed to pay $4.3 billion in civil and criminal penalties in the case brought by the Justice Department. The penalties were part of $22 billion in settlements and fines that Volkswagen is paying in connection with the cheating scandal and the sale of vehicles that emit harmful levels of pollution.