This Is How Volkswagen's Diesel Emissions Cheat Works, According to ECU Hacker (Video)

Aaron Cole
by Aaron Cole

Volkswagen’s emissions cheating program closely follows a set of parameters that are very similar to those defined by the New European Driving Cycle (NEDC), an engineer said this week.

The cheat exists in the ECU’s “main mode,” said Felix Domke, and triggers a normal dosage of urea and other exhaust controls to bring NOx emissions to within acceptable levels.

Domke presented his findings of an unpacked Volkswagen ECU to the 32nd Chaos Communication Congress in Germany.

His findings are mostly in line with what the automaker has already admitted: its 11 million cars worldwide cheated emissions tests by using two different modes for operation, and that its cars could pollute up to 40 times the legal limit of nitrogen oxides when running normally.

But Domke, who said he owns a Volkswagen Sharan equipped with a 2-liter diesel engine, said his own observations showed a severe change in the ECU’s behavior when it exceeded the bounds of what it considered was an emissions test — more than what’s been reported so far.

Domke said he purchased a Volkswagen ECU online and extracted its millions of lines of code. The VW ECU’s behavior is mostly governed by parameters defined outside of its code — not constants that would be hard-coded into the programming — embedded within the computer’s hardware.

He said the car’s main modes for exhaust management were a “normal mode” and an “alternative mode,” the latter of which mostly dominated the car’s behavior. In his own driving, after observing the state of the car, Domke said he found the car ran in a “cold start” cycle for roughly 20 percent of the time and on its “alternative mode” for nearly 80 percent of his driving. Only a small fraction of his normal, everyday driving was in “normal mode.” During “normal mode,” the selective catalytic reduction system used by Volkswagen would consume significantly more diesel emissions fluid than in “alternative” mode. Domke said that finding was supported by additional observations: his van used far less urea than he anticipated.

Domke said he graphed the European emissions testing cycle and overlaid those results with the upper and lower limits of the ECU’s “normal mode” and discovered that the mode aligned perfectly with the limits.

He didn’t test differences in engine performance, nor could he say whether the cheat applied to cars in other countries. But Domke pointed to a parameter in the engine’s code that seemingly always initiated its “alternative” exhaust program: the outside temperature would only need to be suitable for life to exist — above -6,357.9 degrees Fahrenheit (-3,550 degrees Celsius).

Only after a fairly specific set of conditions were met: atmospheric pressure, temperature, speed and distance, which coincide with the NEDC testing parameters, would the car begin its “normal” cycle.

Domke presented his work with Daniel Lange, a former BMW engineer who said the likelihood that the ECU was developed by a “small group” of Volkswagen engineers is hard to believe. Lange said roughly 1,000 hard disks were confiscated from 380 employees, which is hardly a small group.

Also, Lange said the paper trail for documenting changes to an engine’s ECU is prolific — there are too many laws that govern how cars are controlled and automakers fastidiously document those changes for legal reasons.

The presentation is just over 1 hour long. If you want to get to the meaty stuff right away — like how the “defeat device” worked — skip ahead to around 51 minutes in. Otherwise, grab some popcorn.


Aaron Cole
Aaron Cole

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  • Jthorner Jthorner on Dec 31, 2015

    Impressive work Mr. Domke. Too bad VW hasn't learned to just be honest and tell the world what they did, who knew, and who approved it. The ongoing body part covering attempts out of VW are just more of the same ill behavior that got them into this mess in the first place.

    • Kendahl Kendahl on Jan 01, 2016

      You are assuming that VW is a monolithic organization with everyone on the same page. Right now, I'm sure that VW resembles a roach infested room just after the lights are turned on. Everyone is running for cover and cooperating as little as possible. One of the weaknesses of autocratic, top-down organizations, like VW, is that dissent and disaffection are never resolved. They just go underground and fester.

  • Shaker Shaker on Jan 01, 2016

    This reminds me of the early days of catalytic converters; introduced to clean up carbureted, and (then poorly-controlled) throttle-body fuel injection systems, when certain conditions would result in the converter being swamped with hydrocarbons. The result of this would be a drastic increase in emissions (that "rotten egg" smell) and the converter actually overheating enough to trigger a warning light. Once multi-port FI and better computer control became available, catalytic converters became more effective (and smaller) since they had many fewer excess hydrocarbons to "convert". We're near the point when the low-end torque requirements of normal driving can be met by battery-hybrid systems (in light vehicles) and pneumo-hydraulic hybrid (for larger trucks with frequent stop-and-go operation) to replace the diesel engine - the continued development of more energy-dense batteries and stronger materials (for hydraulic accumulators) will supplant the need for diesel engines - but the specter of economics is still (somewhat) in favor of cleaning up the crud as it is produced.

    • See 4 previous
    • Lack Thereof Lack Thereof on Jan 02, 2016

      @golden2husky A lot of cars from the 70's (including a Porsche product I owned) had warnings in their owners manuals saying things like "Do not idle the car with a cold engine. Drive immediately upon starting." This is exactly why. Allowing the car to idle for several minutes with the choke set or the cold-start injector switched on would dump enough extra fuel/soot into the catalytic converters to be a fire hazard. Driving it immediately would warm the engine faster and thus shut off the choke faster. My Porsche would actually shut off and refuse to restart for several minutes if you tried to warm it up in the driveway on a cold morning for more than a minute or two.

  • Michael Gallagher I agree to a certain extent but I go back to the car SUV transition. People began to buy SUVs because they were supposedly safer because of their larger size when pitted against a regular car. As more SUVs crowded the road that safety advantage began to dwindle as it became more likely to hit an equally sized SUV. Now there is no safety advantage at all.
  • Probert The new EV9 is even bigger - a true monument of a personal transportation device. Not my thing, but credit where credit is due - impressive. The interior is bigger than my house and much nicer with 2 rows of lounge seats and 3rd for the plebes. 0-60 in 4.5 seconds, around 300miles of range, and an e-mpg of 80 (90 for the 2wd). What a world.
  • Ajla "Like showroom" is a lame description but he seems negotiable on the price and at least from what the two pictures show I've dealt with worse. But, I'm not interested in something with the Devil's configuration.
  • Tassos Jong-iL I really like the C-Class, it reminds me of some trips to Russia to visit Dear Friend VladdyPoo.
  • ToolGuy New Hampshire
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