WSJ editorial

…According to EPA, a software switch senses whether the car “is being tested or not based on various inputs including position of steering wheel, vehicle speed, the duration of the engine’s operation and barometric pressure” and these “inputs precisely track the parameters of the federal test procedure.” Under normal driving conditions, the switch activates a separate engine calibration.

In other words, the cars are electronically programmed to produce compliant emissions results only during government testing. On highways and streets, they spew 10 to 40 times as much as allowed under U.S. law.

Defeat devices aren’t new or a diabolical German invention. As EPA notes, mechanisms that deactivate emissions controls may serve a legal purpose if they protect vehicles against damage. But manufacturers are then required to disclose to regulators their presence in certification applications, which VW didn’t.

Two decades ago GM had to cough up $45 million for installing defeat devices in nearly half a million cars that overrode carbon monoxide controls. In 1998 seven U.S. manufacturers of heavy-duty diesel engines, including Caterpillar and Volvo Truck, settled federal charges of implanting devices that disabled NOx controls for $1 billion.

What regulators don’t ever explain is that these defeat devices serve a functional purpose, which is usually to increase performance and fuel efficiency. They want to pretend that emissions regulations are a clean, free ride. Until now, VW—which advertised its environmental friendly and powerful engines—was in on the charade.

Auto experts have posited that VW’s defeat device was intended to boost fuel economy and torque, which are two big draws of modern diesel cars. VW’s 2015 Passat gets 44 miles per gallon on highways. Trouble is, engines that are designed to burn more efficiently—and therefore emit less carbon—release more NOx. They also have less oomph. EPA and CARB should fess up to this trade-off, and the wrongdoing involved ought to be precisely identified.

The immediate upshot is that VW will have to recall the lemons to bring them in compliance with government rules. Any fix will likely cost several thousand dollars per vehicle, reduce performance and increase carbon emissions. Will drivers even want the government’s clean bill of health?

VW deserves to pay for any intentional wrongdoing, but the rest of the industry and the country need to know whether this is the great deception that EPA alleges or the kind of well-known regulatory trade-off that is being harshly punished for the first time.