James Liang worked for Volkswagen’s Wolfsburg plant while he developed diesel engines. (credit: Bruno Kussler Marques)

Volkswagen Group has been beset by scandal since last September, when the Environmental Protection Agency (EPA) made public that VW had been including illegal software in diesel Volkswagens and Audis. The software detected when the cars were being tested in a lab so that they could pass emissions tests, but once the cars hit real-world conditions, the software circumvented the emissions control system to spew large amounts of nitrogen oxide (NO_x) into the atmosphere.

According to the plea agreement (PDF), in 2006 Liang and others began building the EA 189 diesel engine that has been the center of the controversy. When the engineers realized they couldn’t meet consumer expectations and US air quality standards at the same time, they began looking into using illegal software (often known in the auto industry as a “defeat device”). By 2008, Liang worked to “calibrate and refine the defeat device.” Later that year, he moved to the US to help with “certification, testing, and warranty issues” for the company’s new diesels.