The law firm that previously sued Volkswagen, Mercedes Benz, and Fiat Chrysler for alleged cheating on diesel emissions says General Motors did the same thing.
Hagens Berman has sued GM on behalf of a potential class of approximately 700,000 owners of Chevy and GMC diesel trucks, claiming the automaker cheated to bypass federal standards for allowable emissions of nitrogen oxides (NOx.)
The U.S. EPA says the pollutants are linked to asthma, heart disease, smog and global warming, among other ills.
"They marketed these diesels as clean and having low emissions," says attorney Steve Berman, "and it turns out they have defeat devices. That's a device that senses when the vehicle is being tested, and when the vehicle is being tested, the emissions control systems go on, and when they're out of those parameters, the system is de-rated, the emissions controls are turned down."
Berman says after the Volkswagen diesel emissions scandal broke, he didn't believe it was limited to that one automaker. So his firm has had a team testing diesel cars made by Mercedez Benz, Fiat Chrysler, and General Motors "for a long time."
Berman's team uses portable emissions measurement systems, or PEMS, to test the vehicles' real-world emissions on the road, as opposed to those captured in laboratory conditions during government tests.
In a statement, GM says, "These claims are baseless and we will vigorously defend ourselves. The Duramax Diesel Chevrolet Silverado and GMC Sierra comply with all U.S. EPA and CARB emissions regulations."
Meanwhile, the U.S. Justice Department sued Fiat Chrysler over allegations of diesel emissions this week.
The U.S. EPA did not respond to an inquiry about whether it was investigating GM over the issue.