The German automaker's shares have lost almost a quarter of their value after it admitted using its DRM'd computer system to hide how much pollution its engines emit.
VW halted sales of the models involved on Sunday and said it's cooperating with the probe and ordered its own external investigation into the issue. Winterkorn, who has led the company since 2007, said he was "deeply sorry" for breaking the public's trust and that VW would do "everything necessary in order to reverse the damage this has caused."
Winterkorn, whose contract renewal is scheduled for a supervisory board vote on Friday, now faces a serious challenge to his leadership, said Arndt Ellinghorst, a London-based analyst for Evercore ISI.
"This latest saga may help catalyze further management changes at VW," Ellinghorst wrote in a note Monday.
The U.S. charges are "grave" and must be clarified swiftly, said Stephan Weil, prime minister of the German state of Lower Saxony, which owns 20 percent of Volkswagen's voting shares. "Possible consequences can be decided after that."
A stark reminder that the point of Rights Management is to manage your rights.