Whoops: Mercedes-Benz Diesel Probe in U.S. Uncovers Possible Defeat Device

2017 Mercedes-Benz C350e grille hood ornament - Image: Mercedes-Benz

U.S. investigators have found what could be illegal software modifications on Mercedes-Benz diesels intended to help the vehicles pass emissions testing. An engine management function called Slipguard recognized whether the car was undergoing testing procedures while another, called Bit 15, halted emissions cleaning after roughly 16 miles of driving. Together, the two pieces of software may amount to what is known within the industry as a “defeat device.”

When paired the software apparently enabled the cars to produce NOx levels up to 10 times higher than what is legally permitted. Interestingly, Mercedes-Benz issued a voluntary recall upon roughly 3 million European cars last month to reduce nitrogen oxide emissions by tweaking their electronic control units. 

German media outlet Bild am Sonntag, has also cited confidential emails between Mercedes’ engineers that questioned whether the software functions were legal to use. Daimler has been under pressure in the diesel exhaust scandal for some time. Stuttgart prosecutors and the U.S. Department of Justice have both been investigating the issue since the spring of 2017.

A company spokesman declined to elaborate on the documents, saying the automaker was cooperating with the U.S. authorities and had agreed upon strict confidentiality with the Department of Justice. “The authorities know the documents and no complaint has been filed,” a spokesman told Automotive News. “The documents available to Bild have obviously selectively been released in order to harm Daimler and its 290,000 employees … We have been fully cooperating for more than two years and provide comprehensive transparency.”

Daimler CEO Dieter Zetsche has repeatedly emphasized, since the outbreak of Volkswagen’s diesel sandal over two years ago, that vehicles from Mercedes-Benz had not and would not be manipulated.

[Image: Mercedes-Benz]