VW dropped into its biggest crisis ever following last week’s disclosure that stealth device was used in its diesel cars to cheat U.S. testers.
A Volkswagen technician alerted the company in 2011 about the software, which enables vehicles to pump out more pollutants than allowed by regulators, authority reported.
Winterkorn, who had been VW’s CEO since 2007, said he took responsibility for the scandal and stepped down on Wednesday.
Matthias Mueller, the head of VW’s Porsche unit, took over for Martin Winterkorn as chief executive, hoping that the successor will help the company recover from the crisis.
VW was facing “unprecedented challenges” and promised a full investigation into the scandal.
Earlier this week, Volkswagen admitted that 11 million of its diesel cars are equipped with devices that can cheat pollution tests.
Afterwards, authorities in France and South Korea announced probes into Volkswagen over rigged emissions tests.
Similar investigations have been launched across the European Union, in Canada, in India and in Australia.