It is not Volkswagen’s first run-in with regulators over emissions.
When the United States began regulating tailpipe pollutants in the 1970s, Volkswagen was one of the first companies caught cheating.
It was fined $120,000 in 1973 for installing what became known as a “defeat device,” technology to shut down a vehicle’s pollution control systems.
This time, it equipped its vehicles with software that was programmed to fake test results, an action the E.P.A. rebuked in 1998, when it reached a $1 billion settlement with truck-engine manufacturers for doing the same thing.
Over the last year, when confronted with evidence that its system was not performing as promised, Volkswagen aggressively pushed back, saying that regulators were not doing the testing properly.
In 2007, Mr. Winterkorn attracted little attention when he made his first trip to Detroit as Volkswagen’s chief executive, during the industry’s annual auto show there.
The company was then a bit player in the United States. There was more excitement about Changfeng Motor, the first Chinese automaker to participate in the show.
One Volkswagen executive did make headlines — but he was not there.
Wolfgang Bernhard, head of the Volkswagen brand, was a well-known figure in Detroit, having spent several years as the second-highest-ranking executive at Chrysler, then part of Daimler.
He was remembered for dressing in black leather during one auto show while he rode a four-wheel, 500-horsepower motorcycle called the Dodge Tomahawk.
Mr. Bernhard was widely expected to resign in a corporate shake-up, and he did a few days later. His departure set off ripples not just in Volkswagen’s boardroom, but also under the hoods of its future diesel vehicles.
Mr. Bernhard, a longtime Daimler executive, previously announced a deal to use a technology called BlueTec, which was developed by Mercedes, a division of Daimler, and Bosch, a German supplier.
BlueTec mixes a chemical known as urea with engine exhaust to neutralize nitrogen oxide, one of the most harmful diesel pollutants. While it is an effective system, it can be costly and requires drivers to periodically top up a tank of urea.
A few months after Mr. Bernhard’s departure, the plan was scrapped. The trade publication Automotive News quoted an Audi executive saying Volkswagen’s own technology was strong enough. “We don’t need BlueTec,” the executive said.
There have been no suggestions to date that BlueTec vehicles sold by Mercedes violate emissions standards.
Matt DeLorenzo, a diesel expert and the managing editor at Kelley Blue Book, said it was not surprising to the industry at the time that Volkswagen abandoned BlueTec for its small and midsize cars in favor of a system that would not require the unwieldy, expensive urea tank. (Volkswagen uses its own urea-based system for heavier vehicles like the Touareg S.U.V.)
“Volkswagen wanted to make the diesel ownership experience as easy as possible, akin to having a regular gas engine,” he said.
