Enough is enough already.

With the United States' Environmental Protection Agency (EPA) and California Air Resources Board (CARB) having rejected Volkswagen's proposed fix for an estimated 580,000 vehicles affected in the country by its emissions scandal, the automaker's second-largest shareholder is giving the company three months to come clean about the origins of its diesel vehicles' manipulation.

"There is a very legitimate concern on the part of U.S. authorities, the public and the company itself for a comprehensive investigation," Stephan Weil, VW's supervisory board member and Lower Saxony's prime minister, said in an interview, as reported by Bloomberg. "It's in the interest of VW to provide a complete clarification."

The deadline would see to it that VW makes good on its promise of reporting its emissions scandal's roots during the company's annual shareholders' meeting on April 21. To prepare for that revelation, United States law firm Jones Day was hired by the automaker last year to independently get to the bottom of how VW cheated.

In addition, the automaker followed that in December by commissioning Ken Feinberg, who oversaw funds restitution programs for General Motors' defective ignition switches and BP's oil spill, to guide a similar refund program for affected owners of manipulated vehicles in the United States.

This deadline comes days after the company publicly stood by CEO Matthias Mueller, refuting rumored reports that it would be letting him go.

Will all those things add up to finally unearthing the roots of VW's emissions crisis?

It better, because Forbes is reporting that the Department of Justice's federal lawsuit against VW for disregarding the Clean Air Act can result in regulatory fines up to $18 billion in the U.S. alone.

The embattled automaker coming clean would probably ensure that the projected sum of fines doesn't get worse.