Responding to EPA Allegations, VW Admits to Installing “Defeat Devices” on Diesel Engines

On September 18, 2015, EPA issued a notice of violation of the Clean Air Act to German automaker Volkswagen (VW), for knowingly installing “defeat devices” in the engines of 482,000 four-cylinder VW and Audi diesel vehicles sold from model years 2009 to 2015. MJB&A analysis found that these vehicles have likely resulted in more than 42,000 tons of excess NOx emissions. Further investigation and emissions testing found additional vehicle models had installed similar defeat device software, and resulted in EPA issuing a second notice of violation on November 2, 2015. This issue brief explains the defeat device software, the resulting excess NOx emissions, and potential ways VW can fix the problem.