(September 24, 2015) Volkswagen CEO Martin Winterkorn stepped down Wednesday, taking responsibility for the German automaker's rigging of U.S. diesel emissions tests. Winterkorn had been under heavy fire since revelations Friday that the company was cheating on tests by fitting its diesel vehicles with software that masked their real-world emissions, in violation of the U.S. Clean Air Act.

The pressure intensified this week as the company announced that some 11 million vehicles worldwide had the illegal software.

Under Winterkorn’s leadership, VW was closing in on Toyota Motor Corp. as the world’s biggest automaker, with the German manufacturer overtaking its Japanese competitor in global sales in the first half of the year.

VW’s six-month sales amounted to 5.04 million cars and trucks, exceeding Toyota’s 5.02 million deliveries. VW has a goal of becoming the No. 1 carmaker by 2018.

Winterkorn, who took over as CEO in 2007, led a turnaround that propelled VW from an also-ran that had cut 20,000 German jobs under his predecessor to a global powerhouse with about 600,000 employees that included a stable of 12 brands from Lamborghini supercars to Scania heavy trucks.

He has expanded aggressively, boosting the number of production sites around the world to more than 100 locations, with an emphasis on China and North America.

Winterkorn announced his resignation in a statement released Wednesday:

 "I am shocked by the events of the past few days. Above all, I am stunned that misconduct on such a scale was possible in the Volkswagen Group.

As CEO I accept responsibility for the irregularities that have been found in diesel engines and have therefore requested the Supervisory Board to agree on terminating my function as CEO of the Volkswagen Group. I am doing this in the interests of the company even though I am not aware of any wrong doing on my part.

Volkswagen needs a fresh start — also in terms of personnel. I am clearing the way for this fresh start with my resignation.

I have always been driven by my desire to serve this company, especially our customers and employees. Volkswagen has been, is and will always be my life.

The process of clarification and transparency must continue. This is the only way to win back trust. I am convinced that the Volkswagen Group and its team will overcome this grave crisis."

Sources: Volkswagen, Automotive News