"That legal assessment of the defeat device scandal seems to have held up as the researchers analyzed the cars’ code. The VWs and Audis in question checked for a number of parameters at startup, and if a lab test was a possibility, the car would start with that assumption, enabling full emissions controls. The code permitted the car “to operate... as if two distinct personalities took turns controlling the vehicle,” the paper’s authors wrote.

The paper also notes that the researchers tested the diesel Fiat 500X because it used the same Engine Control Unit from Bosch as the Volkswagens and Audis did. There was no mention of the “acoustic condition” in the Fiat’s function sheet, but some undisclosed code was discovered controlling how the car regenerates its NOx Storage Catalyst (NSC).

“Unlike the Volkswagen defeat device, the FCA [Fiat Chrysler Automobiles] mechanism relies on time only, reducing the frequency of NSC regenerations 26 minutes 40 seconds after engine start,” the paper notes. In a normal system, the NSC reduces NOx emission by trapping it in a catalyst and then regenerating the catalyst as it gets full.

But regeneration hurts a car’s fuel economy numbers and puts a lot of load on the Diesel Particulate Filter (DPF). “By reducing the frequency of NSC regeneration, a manufacturer can improve fuel economy and increase DPF service life, at the cost of increased NOx emissions,” the researchers explained."

"So next time you get in your car, look around. Think about the things you do and don’t like about your car. Realize that nothing in your car exists because one engineer didn’t get enough sleep and decided to put that USB charger just out of your grasp. Designing a car is an immensely complex, exhausting process and each part has its own story. Try to understand how all those stories come together to make one coherent, attractive, quality, affordable, safe vehicle, and you’ll understand the challenge of my job."