What we know about Volkswagen's diesel-cheating hack

Volkswagen's hack to allow its cars to violate pollution laws by cheating on emissions testing is a lot more sophisticated than it first appeared. Here's what we know now, including links to the documents that first discovered the cheating.

First, a bit of background. The cheating was not an incidental piece of work -- it was at the core of Volkswagen's plan for worldwide automotive dominance. The New York Times reports that Volkswagen had a plan to become the world's largest automaker by 2018, and that expanding the sales of diesel cars was one of its centerpieces. The Times notes, "One way Volkswagen aimed to achieve its lofty goal was by betting on diesel-powered cars -- instead of hybrid-electric vehicles like the Toyota Prius -- promising high mileage and low emissions without sacrificing performance."

There was a big problem with that strategy, though: Volkswagen didn't want to do the actual hard work of making its diesel cars offer high performance and high mileage while meeting emissions standards. The company abandoned a pollution-control technology called BlueTec, developed by Mercedes, because it was expensive and requires drivers to have a topped-up tank of urea.

Instead, Volkswagen hacked its cars to violate pollution laws by cheating on emissions testing, and not for the first time. When the U.S. began regulating pollutants back in the 1970s, it installed a "defeat device" to cheat on government pollution tests, and was fined $120,000 for it.

So how does Volkswagen's latest cheating work? As has been reported, its cars' computing systems turn off the full-pollution control system when cars are being driven. Only when the cars are being tested is the pollution control system turned on.

That requires more work than you might think. It requires the use of a hidden mode that car owners don't see called Dyno Mode or Test Mode. The cheating was first uncovered back in 2014 when the state of California was running pollution tests on diesel cars with a non-profit group called the International Council on Clean Transportation. The testing showed that when on the road, in normal driving conditions, the cars were heavy polluters. However, when the cars were run on a "car treadmill" known as a dynamometer, there was much less pollution. A lab called CAFEE did the testing that found this out.

California notified the EPA, which opened an investigation. When the EPA questioned Volkswagen, the car company answered by attacking the findings. Arvind Thiruvengadam, a CAFEE investigator who had helped uncover the problem, told the New York Times, "They tried to poke holes in our study and its methods, saying we didn’t know what we were doing They were very aggressive." Volkswagen engaged in similar tactics for months.

Eventually, investigators discovered the Volkswagen hack that used Dyno Mode or Test Mode. When a car is on a dynamometer, only the car's front wheel moves, while the back ones are stationary. Because of that, Consumer Reports says, the car's software might interpret that as a dangerous driving situation and activate traction control or stability control. So the car's software uses a variety of sensors to see whether to put the car into Test Mode.

That's not abnormal --- other auto makers have similar modes. What is abnormal is that Volkswagen programmed its cars to only use its emission control system properly when in Test Mode. The rest of the time, the anti-pollution system was programmed not to work properly, and the car spewed dangerous pollutants. Volkswagen did this because emissions control affects a car's performance.

Here's a link to the EPA's finding. It's well worth a read, not only for the technical details, but because it traces Volkswagen's lying. It finds that only after the hack was found, "did VW admit it had designed and installed a defeat device in these vehicles in the form of a sophisticated software algorithm that detected when a vehicle was undergoing emissions testing."

If you want even more details, here's the original 133-page report from CAFEE that did the original testing and uncovered the problem.

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