The German government has given VW until October 7 to explain how it will resolve the scandal, which has rocked the industry and wiped USD 33 billion, or 38 per cent, off VW's market value in 10 days.
Chief executive Matthias Mueller, who took over the Volkswagen steering wheel on Friday, told senior management that technical solutions would be submitted in October.
Once approved by the German authorities, Volkswagen will inform customers and arrange for the cars to be refitted, he told managers late yesterday, according to remarks released by the firm.
They then switch off the controls when the car is on the road, allowing it to spew out harmful levels of emissions.
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CEO Mueller insisted that the software was not activated in all 11 million vehicles, however, and the number of vehicles actually needing a refit would be fewer than that.
Nevertheless, with the embattled auto maker facing incalculable costs and a potential tidal wave of litigation, CEO Mueller described the crisis as "the severest test in (VW's) history."
"The inconceivable misconduct that has come to light in Volkswagen over the past days pains me and angers me immensely," Mueller said.
VW's upmarket subsidiary Audi and its Czech arm Skoda have admitted that more than three million of their vehicles were fitted with the suspect devices. Spanish unit Seat has said 700,000 of its cars were also equipped with the technology.
A spokesman for VW's trucks division said that 1.8 million light commercial vehicles were involved.
The carmaker, which in the first six months of this year overtook Toyota to become the world leader in terms of sales, needed to win back the trust it has lost, he said.