May 25 (UPI) -- General Motors on Thursday became the third automaker in the last two years to be accused of installing software on diesel vehicles that allowed them to beat U.S. emissions law.
A Seattle-based law firm filed a civil lawsuit against the U.S. automaker in Michigan court on Thursday, alleging that GM presently has about 700,000 diesel vehicles on the road in the United States that are equipped with the so-called "defeat devices."
"Defeat device" software tells the vehicles to run at government-mandated emissions levels when it's being tested. Once the vehicles leave the shop, though, they resume emitting at levels that exceed EPA standards.
Thursday, the automaker denied the suit's accusations.
"These claims are baseless and we will vigorously defend ourselves," GM said in a statement. "The Duramax Diesel Chevrolet Silverado and GMC Sierra comply with all U.S. EPA and CARB emissions regulations."
The nearly 200-page complaint says GM installed what it called "unlawful, unfair, deceptive, and otherwise defective emission controls."
The vehicles covered in the suit are diesel versions of the 2011-16 GMC Sierra 2500 and 3500 HD trucks and Chevrolet Silverado 2500 and 3500 HD pickups. The plaintiffs said the trucks were outfitted with the software because they were not able to achieve the fuel economy GM promised.
GM is the second automaker this week to be accused of skirting the U.S. Clean Air Act, which lays out regulations for vehicle emissions.
Tuesday, a similar complaint was lodged against Fiat Chrysler for about 100,000 of its diesel Dodge Ram trucks and Jeep Grand Cherokee sport-utility vehicles made between 2014 and last year. Fiat Chrysler also denied the claims.
Last year, Volkswagen AG agreed to a nearly $3 billion settlement with the Department of Justice over "defeat devices" it had installed in a half-million U.S. diesel vehicles between 2009 and 2015.
The law firm behind the suit said GM's violations are even larger than Volkswagen's.
"This is a shocking discovery, and a really big deal because the [nitrous oxide] limits for these big trucks are four times what the limits were for the much smaller Volkswagen passenger cars -- and there are more of these trucks on the road," attorney Steve Berman said.
German auto parts manufacturer Bosch was also named in the suit.