• 2001-2013: LEU-based clean air group ICCT* monitors carbon dioxide (CO2) emission levels of 540,000 diesel cars. Gap between actual CO2 levels and manufacturers'claims rises to 38 %.
  • 2013-2014: Joint ICCT and West Virginia University project in U.S. compares real-world tests on VW cars with lab tests by CARB. Results show nitrogen oxides (NOx) emissions and exceed lab tests by up to 35 times.
  • May 2014: U.S. Environment Protection Agency (EPA) opens investigation into Volkswagen.
  • December 2014: VW installs software patch to Engine Control Module (ECM) which operates engine and pollution control technology.
  • May 6, 2015: CARB begins testing cars with software patch-NOx emissions remain higher than U.S. limits.
  • July 2015: Regulators refuse to certify VW's 2016 models for sale in U.S. unless company explains anomalous emission levels.
  • September 3, 2015: VW admits to CARB and EPA that it cheated on emission tests.