The suit accuses the company of using software that helps the diesel versions of Chevrolet Silverado 2500HD and GMC Sierra 2500HD heavy-duty pickup trucks with Duramax engines meet emissions requirements.
The software was used in about 705,000 trucks sold from 2011 to 2016, the suit says. It argues G.M. deceived customers by marketing the vehicles as “clean” diesel trucks and seeks to force the company to buy the vehicles back and compensate owners for economic losses.
According to the suit, the trucks conform to emissions standards when they are being driven at steady speeds and when outdoor temperatures range from 68 to 86 degrees — the conditions used for some of the emissions testing such trucks undergo.
Absent those conditions, the vehicles emit four to five times the pollutants than are allowed, the suit says. It alleges that G.M. intentionally programmed the vehicles’ emissions controls to pass emissions tests and to then scale back those controls in real-world conditions to improve power and fuel-economy.
In response to the suit, G.M. said heavy-duty trucks with its Duramax diesel engine complied with all emissions regulations of the Environmental Protection Agency and the California Air Resources Board, which plays an influential role in vehicle emissions.
The E.P.A. did not respond to requests for comment on the suit. The California agency is reviewing the lawsuit, a spokesman said. He declined further comment.
The suit was filed by Hagens Berman Sobol Shapiro, a law firm that specializes in class actions and that previously filed a diesel-emissions suit against G.M. related to the Chevrolet Cruze compact and another against Fiat Chrysler; those suits are pending. A similar suit filed by the firm against Mercedes-Benz was dismissed. Hagens Berman has also filed liability claims unrelated…