How VW Tricked the EPA

By now you've probably heard that Volkswagen installed software in a number of its diesel vehicles that allowed them to cheat emissions testing and spew up to 40 times the legal amount of gunk into the air. But how'd they actually do it? It's apparently pretty simple. Anna Stefanopolou, professor of mechanical engineering at the University of Michigan, tells Wired the company installed computer sensors in the steering column of its diesel vehicles. During normal driving, you turn the steering column and the car's wheels turn. But during emissions testing, the wheels turn without the steering column moving. Stefanopolou says that was likely the signal to turn the car's catalytic scrubber up to full power.

Wired reports catalytic scrubbers—when they're actually turned on—cut emissions from diesel engines by up to 90%. Those emissions include nitrogen oxides, which become ozone and create smog when exposed to sunlight. They've been linked to asthma attacks and respiratory illnesses and are just generally really bad for humans. According to Volkswagen, approximately 11 million of its diesel vehicles worldwide are affected. "We have totally screwed up," one executive admitted. The company is facing up to $18 billion in fines in the United States alone. (More Volkswagen stories.)