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General Motors hit with diesel emissions cheating lawsuit

Published 26 May 2017

General Motors (GM) has been accused of using a device in its diesel-powered vehicles in order to cheat on emissions tests, similar to Volkswagen scandal.

A group of more than 700,000 owners and lessees of GM’s Chevrolet Silverado and GMC Sierra Duramax-based diesel engines filed a lawsuit in a federal district court in Detroit.

It alleges that the two heavy-duty trucks emit two to five times than the legal limit of dangerous NOx pollutants in real-world driving, the lawsuit claimed.

German auto parts-maker Bosch has also been included in the lawsuit for allegedly supplying defeat devices to GM.

The models under question include 2011-2016 GMC Sierra 2500 HD and 3500 HD trucks, and GM Silverado 2500 HD and 3500 HD trucks.

As per the lawsuit, the trucks comply with emissions standards when they are being tested at steady speeds and when outdoor temperatures range between 68 to 86F, the conditions used for the testing undergo changes.

When these conditions are absent, the vehicles emit between two to five times the pollutants than are allowed. GM has used at least three defeat devices in its Duramax diesel engines. By reversing the traditional order of the exhaust treatment components and putting the Selective Catalytic Reduction (CSR) in front of the Diesel Particulate Filter (DPF) and GM could obtain and market higher power and efficiency from its engines while still passing the cold-start emissions certification tests.

Reordering would drastically increase the need to employ Active Regeneration and other power and efficiency sapping exhaust treatment measures, which reverse the very advantage gained.

Thus, the company installed defeat devices to purposefully reduce SCR dosing, increase NOx emissions and thus increase Active Regeneration.  This process, the lawsuit stated that will increase the NOx emissions from two-fold to five-fold.

General Motors has however denied the allegations. The company said: "These claims are baseless and we will vigorously defend ourselves.  The Duramax Diesel Chevrolet Silverado and GMC Sierra comply with all US Environmental Protection Agency (EPA) and California Air Resources Board (CARB) emissions regulations."


Image: Lawsuit filed against GM for allegedly installing ‘defeat devices’ in pickup trucks. Photo: Courtesy of General Motors.