GM Truck Diesel Defeat Device Investigation

Trucks with Duramax Diesel Engines May be Rigged to Pass Emissions Tests

Gibbs Law Group’ automotive lawyers are investigating allegations that General Motors rigged diesel engines in its Silverado and Sierra HD trucks to pass emissions tests. An initial class action was filed Thursday, May 25, 2017, and additional suits may be filed in the coming weeks. Call (800) 254-9493 or fill out the form to get a free consultation with our nationally recognized auto attorneys, free.

Own a ’11-’16 FM Sierra or Silverado Truck?

The specific trucks named in the suit are the model year 2011-2016 GM Sierra 2500 HD and 3500 HD trucks, and GM Silverado 2500 HD and 3500 HD trucks. The suit alleges that GM placed emissions test defeat devices in 705,000 of these heavy-duty trucks, all of with are equipped with Duramax diesel engines.

Per the suit, the trucks emit two to five times the legal limit of dangerous NOx pollutants in real-world driving. News reports state that upon news of the filing, shares of GM fell as much as 2.7 percent (with the stock later recovering some of its losses).

Pattern of Automaker Emissions Violations

The suit against GM follows similar lawsuits, investigations, and government actions against other manufacturers. Most prominently, Volkswagen agreed to pay billions of dollars to settle a defeat device scandal. Chrysler has also been subject to such allegations: “Once again, a major automaker made the business decision to skirt the rules and got caught,” said CARB Chair Mary D. Nichols. “CARB and U.S. EPA made a commitment to enhanced testing as the Volkswagen case developed, and this is the result of that collaboration.”

The existence of a defeat device in your truck could impact its value and your registration. Call (800) 254-9493 or fill out the form to get a free consultation with our nationally recognized auto attorneys, free.

How Emissions-Cheating Software Works

Emissions-cheating software can take different forms. They may turn off emission controls on vehicles to improve performance when they are in normal operation—as opposed to during testing. In a number of instances, drivers have alleged that defeat devices have been designed to automatically turn back on when the vehicle senses it is being hooked up to emissions testing equipment.

The suit against GM alleges three defeat devices:

GM Defeat Device No. 1 reduces or derates the emissions system when temperatures are above the emissions certification test range (86°F). GM Defeat Device No. 2 operates to reduce emissions control when temperatures are below the emissions certification low temperature range (68°F). Testing reveals that at temperatures below 68°F (the lower limit of the certification test temperature), stop and go emissions are 2.1 times the emissions standard at 428 mg/mile (the standard is 200 mg/mile). At temperatures above 86°F, stop and go emissions are an average of 2.4 times the standard with some emissions as high as 5.8 times the standard. Based on temperatures in the top 30 metropolitan areas, these vehicles are operating with the emissions systems derated a material amount of their vehicle miles travelled. But the emission scheme is a step more nefarious: enter GM Defeat Device No. 3, which reduces the level of emissions controls after 200-500 seconds of steady speed operation in all temperature windows, causing emissions to increase on average of a factor of 4.5. Based on a study of temperatures in 30 major metropolitan areas as well as the demographics of Silverado sales, it is estimated that due to the temperature-triggered defeat devices, the vehicles operate at 65-70% of their miles driven with emissions that are 2.1 to 5.8 times the standard.

Harmful NOx Emissions

Defeat devices can increase vehicles’ emissions of nitrogen oxides (NOx), which cause air pollution, exacerbated breathing conditions, and other harmful health effects. NOx accounts for approximately 8% of the warming impact of current human greenhouse-gas emissions, according to the Intergovernmental Panel on Climate Change.