Dieselgate: how Volkswagen taught its engines to recognise a test and behave
Volkswagen's diesel cars were clean only when they knew someone was watching. Software sensed a laboratory test and switched on full pollution controls, then let nitrogen oxides pour out on the road at up to 40 times the permitted level. A small university road test unravelled it, and the bill passed $33 billion.
The root was an engineering headache. Diesels burn fuel efficiently and emit less carbon dioxide than petrol engines, but untreated they produce 20 times more nitrogen oxides, and the catalytic converters that work on petrol cars do little for them. In 2005 Volkswagen licensed Mercedes' urea-based BlueTec system, but it was costly, fussy and bulky for compact models like the Golf and Jetta, so in 2007 the company dropped it for a cheaper lean NOx trap of its own. That trap could not deliver both good mileage and legal emissions, and engine control units were programmed to spot a test and switch into compliant mode.
Around 11 million cars from the 2009 to 2015 model years carried the software, including 500,000 in the United States, where the limit of 0.043 grams per kilometre was among the world's strictest. Volkswagen advertised its diesels as clean and even collected green car subsidies and tax breaks.
The unravelling began in 2013, when the International Council on Clean Transportation hired West Virginia University researchers to measure diesel emissions on real roads in California. Two of three cars they tested produced excess nitrogen oxides, and both were Volkswagens. The findings reached regulators in May 2014, and in September 2015 the Environmental Protection Agency formally accused Volkswagen of breaking the Clean Air Act.
The share price lost a third within days, chief executive Martin Winterkorn resigned, and several senior engineers were suspended. An American civil settlement of as much as $14.7 billion followed in June 2016; Volkswagen pleaded guilty to criminal charges in January 2017 and was fined $2.8 billion that April. Winterkorn was charged with fraud and conspiracy in May 2018. By June 2020 the total had reached $33.3 billion. Wider testing showed many brands' diesels exceeded limits on the road, and warnings had surfaced years earlier, including a 1998 Swedish critique of Europe's test cycle.
Source: Volkswagen emissions scandal
