How Volkswagen was caught

Andrew Bolt, Herald Sun (Australia)
......to do the first ever evaluation of the tailpipe emissions of diesel cars in America made by European manufacturers.
They tested three cars: a BMW X5, Volkswagen Jetta and Volkswagen Passat, while travelling over 2400kms on each car to get their results.
After driving from Los Angeles to Seattle and back they noticed something odd about their Passat. Going by Volkswagen’s claims, it should easily have let out the least amount of pollution between those three cars — it had a more modern catalytic reduction system which is meant to convert toxic fumes into safer ones — but that wasn’t the case. The nitrogen oxide that came out of the Passat was in fact 20 times more than the baseline levels permitted by the California Air Resources Board.
The team was puzzled. There was no way it could be wrong. They triple-checked the accuracy of their equipment after the Volkswagen Jetta they tested showed readings 30 times more than the claimed pollution rating.
The BMW, though, gave off the exact results they expected.
At the time, the team had no idea why the cars were emitting so much pollution… “...We didn’t point and say, ‘Volkswagen has a defeat device’,” Thiruvengadam told Autoblog. ......"