Currently reading: VW emissions scandal: how Volkswagen's 'defeat device' works
The vehicles affected by Volkswagen's emissions scandal are capable of detecting when they're being tested - here's how

The Environmental Protection Agency's (EPA) official notification issued to Volkswagen on 18 September sheds light on how the company managed to influence the emissions tests with some clever software.

“VW manufactured and installed software in the electronic control module (ECM) of these vehicles that sensed when the vehicle was being tested for compliance with EPA emission standards," the agency explained.

The EPA refers to what it calls a ‘switch’ that enabled the car’s ECM to know when it is being tested on a rolling road: “The ‘switch’ senses whether the vehicle is being tested or not based on various inputs including the position of the steering wheel, vehicle speed, the duration of the engine’s operation and barometric pressure. These inputs precisely track the parameters of the federal test procedure used for emission testing for EPA certification purposes.

“During emission testing, the vehicles’ ECM ran software which produced compliant emission results under an ECM calibration that VW referred to as the ‘dyno calibration’.

“At all other times during normal vehicle operation, the ‘switch’ was activated and the vehicle ECM software ran a separate ‘road calibration’ which reduced the effectiveness of the emission control system. As a result, emissions of NOx increased by a factor of 10 to 40 times above the EPA compliant levels, depending on the type of drive cycle (e.g. city, highway).”

All US vehicles must be issued with a certificate of conformity that proves they adhere to environmental standards.

To obtain a certificate of conformity, a manufacturer must submit a list of all auxiliary emission control devices (AECDs) present on the vehicle. The EPA’s definition of an AECD is “any element of design which senses temperature, vehicle speed, engine RPM, transmission gear, manifold vacuum or any other parameter for the purpose of activating, modulating, delaying or deactivating the operation of any part of the emission control system.”

The issue facing Volkswagen is the switchable system in the ECM was not declared.

“Due to the existence of the defeat devices in these vehicles, the affected Volkswagen vehicles do not conform in all material respects to the vehicle specifications described in the applications for the certificates of conformity that purportedly cover them,” said the EPA.

A defeat device is an AECD “that reduces the effectiveness of the emission control system under conditions which may reasonably be expected to be encountered in normal vehicle operation and use. Motor vehicles equipped with defeat devices cannot be certified.”

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Moparman 23 September 2015

They would have gotten away with it...

If it weren't for those pesky kids! Seriously, the University of West Virginia doing this? It's an okay place and all but the two most-famous people from Morgantown, where the university is situated, are Don Knotts (Barney Fife from The Andy Griffith Show) and Mary Lou Retton of 1984 Summer Olympics fame. Not a hotbed of government stooge conformity. But, then again, the people working there may not be from there, either.
concinnity 24 September 2015

Sticking to facts.

How postmodern of you to focus on the messenger and not the message. It doesn't matter who the people behind the uncovering of a secret are, the real story is what the secret is, what the facts are, what the actual storey is, and who committed the crime.
This story is ALL about how a multinational corporation was caught knowingly and intentionally breaking a clearly stated law, to further it's own profits and those of it's shareholders.And doing this at a cost to the environment and it's own customers health and safety.
Not who found out and what sort of people they might be.
jer 23 September 2015

If they could pass on the rolling road

why turn it off, why not keep that configuration. Was performance effected?
JJ Joseph 23 September 2015

" why not keep that configuration"??

The result was VWs that are identical to European VWs. Performance isn't affected, and they'rfe just as clean as Euro-VWs. The EPA just found a clever way to skewer VW's sales in America. Score one for American industry!
Outoftowner1969 23 September 2015

Clever, though

This has probably come about because they've been set targets they can't achieve within budget. Someone has come up with this cheat as a stop gap and then someone more senior has said, 'fine -job done, money saved, case closed. Move on.' All in German of course.
Straff 23 September 2015


Very funny ;-)