Independent researchers, the California Air Resources Board and the EPA unraveled the Volkswagen ruse over the course of a year.
• International Council on Clean Transportation and West Virginia University researchers alert EPA and CARB to their findings of elevated oxides of nitrogen, or NOx, levels in VW diesels in on-road conditions. EPA and CARB begin investigating.
• VW begins testing to replicate the researchers' findings and investigate causes. In December, VW proposes a recall to make a recalibration fix on about 500,000 vehicles with lean NOx trap or selective catalytic reduction technology. Regulators allow the recall, subject to confirmation that the solution works.
• CARB begins confirmation testing in May on effectiveness of the recall, including in-use monitoring of a 2012 vehicle, and finds that recalibration reduced NOx emissions but not as much as expected. In some cases, the recalibration caused the vehicle to fail the NOx standard.
• In a specially developed test cycle, CARB finds that the recalibration improved the functioning of the selective catalytic reduction emissions control system, but not enough to keep NOx levels from rising.
• CARB shares findings with VW and the EPA in July. In subsequent meetings, VW discloses that its diesel vehicles from the 2009 to 2015 model years have a calibration setting designed to run only during certification testing.
• In a Sept. 3 meeting, VW admits to CARB and EPA staff that the vehicles were fitted with a defeat device that disabled its emissions control systems. Regulators deem the earlier recall unapproved and the vehicles noncompliant.
• The EPA issues a notice of violation to VW on Sept. 18 and announces that its investigation is continuing.
• The EPA announces on Sept. 25 that it will spot-check all light-duty diesel vehicles on the road for emissions defeat devices.
Source: California Air Resources Board, EPA; Bloomberg photos