The casualties keep mounting up in the diesel-emissions scandal, with General Motors coming under fire for allegedly installing defeat devices on over 700,000 vehicles with Duramax engines. A class action lawsuit argues GM and Bosch knowingly sold cars tuned to emit illegal amounts of nitrogen oxide (NOx) when outside the test environment.

According to the lawsuit, Duramax diesels were fitted with three "defeat devices," similar to those used in the now-infamous Volkswagen emissions cheating scandal. When the car was placed in a test environment, the engine would be "de-rated" to meet emissions standards, before defaulting back to a more powerful, less environmentally friendly state of tune out on the open road.

The claim, filed in the U.S. District Court for the Eastern District of Michigan, alleges 705,000 Chevrolet Silverado and GMC Sierra trucks with Duramax diesel engines sold between 2011 and 2016 are fitted with the defeat devices. Bosch, the company which manufactures the chips in GM engines, has also been named as a defendant.

"Increased sales and thus increased profits drove GM to use at least these three defeat devices in its Duramax diesel engines," the complaint states. "By reversing the traditional order of the exhaust treatment components and putting the Selective Catalytic Reduction in front of the Diesel Particulate Filter, GM could obtain and market higher power and efficiency from its engines while still passing the cold-start emissions certification tests."

GM is the latest in a growing line of car companies to be subject to litigation for alleged diesel cheating. Daimler AG had its offices searched by the Stuttgart public prosecutor earlier this week, while the U.S. Department of Justice has filed suit against Fiat Chrysler for "defeat devices" allegedly installed in Jeep and RAM vehicles.

"These claims are baseless and we will vigorously defend ourselves," GM said in a statement today. "The Duramax Diesel Chevrolet Silverado and GMC Sierra comply with all U.S. EPA and CARB emissions regulations."

Source: Hagens Berman, GM