Most automotive scandals affect a single corporation, but Volkswagen's diesel emissions cheating harmed an entire segment. The company's coverup hurt the popularity of diesel-fueled powerplants both in the United States and Europe and forced regulators to take a much more serious look at diesel engine emissions.
The scandal initially broke in the United States when researchers in West Virginia discovered discrepancies between VW's diesel emissions on the road and in the standard lab test. They reported the results to the California Air Resources Board, and the agency investigated further. Eventually, the agency discovered a cheat device where the vehicle lowered its emissions during the standardized evaluation.
The fallout from the scandal forced Volkswagen Group CEO Martin Winterkorn to step down and cost the company over $30 billion in the United States. German prosecutors have also been investigating the company's execs, including recently taking Audi CEO Rupert Stadler into custody over concerns of him possibly suppressing evidence.