Vehicles are subject to various USA emissions tests and it is alleged that Mercedes tailored programs to cheat the specific demands of each evaluation, allowing the diesel engine of Mercedes-Benz models to run in an ultra-clean state, but only for limited periods of time, after which it was then switched into a so-called "dirty mode".
Nearly all major European carmakers have had to answer a few questions, but they weren't all faced with full official investigations.
According to German paper Bild am Sonntag (via Automotive News) citing emails from Daimler's engineers, company employees were questioning whether two engine management functions could be considered defeat devices. Another function, named "Slipguard", is said to have measured speed and acceleration in order to pinpoint when a vehicle was on a dynamometer, which is used to conduct emissions tests. Previously in 2016 a lawsuit was filed against the German brand claiming that its "Clean Diesel" models emit alarmingly high level of nitrogen oxide (NOx) compared to the permitted level.
Mercedes-Benz, Daimler's principal automotive subsidiary, no longer sells cars powered by diesel engines and has no plans to return diesel-powered vehicles to the US market, senior company executives told TheDetroitBureau.com last month.More news: Qualcomm unveils new Snapdragon 845 powered VR headset
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Joerg Howe, a spokesman for the Stuttgart, Germany-based manufacturer, said the documents have "selectively been released in order to harm Daimler and its 290,000 employees".
Software-based engine management systems are illegal if they are not declared to USA regulators and if they are created to evade anti-pollution tests.
A Daimler spokesperson told Reuters the company was cooperating with United States authorities, who knew about the emails, and that Bild had "selectively" released the documents "in order to harm Daimler".
German prosecutors searched Daimler premises in May 2017 as part of an ongoing fraud probe related to false advertising and the possible manipulation of exhaust-gas after-treatment in diesel cars.