Volkswagen made the 2015 admission that it had used software to cheat emissions tests in diesel cars.
The software, known as a defeat device, could detect when a vehicle was undergoing an official laboratory test. During testing, the engine controls reduced nitrogen-oxide emissions. In ordinary driving, the vehicles could emit substantially more pollution than the legal limits permitted.
The U.S. Environmental Protection Agency issued a notice of violation against Volkswagen in September 2015. The company acknowledged that the software had been installed in millions of diesel vehicles worldwide. The scandal damaged Volkswagen’s reputation, led to recalls and legal settlements, and caused senior executive Martin Winterkorn to resign.
The phrase “Dieselgate” is widely used for the affair, but it should not be confused with every later dispute involving diesel vehicles. The central issue was deliberate manipulation of emissions testing through software rather than a simple mechanical defect.