The Volkswagen defeat device: an engineering ethics case study

The notice that broke the story open

On 18 September 2015 the US Environmental Protection Agency issued a Notice of Violation of the Clean Air Act to Volkswagen AG, Audi AG and Volkswagen Group of America, alleging that certain diesel vehicles contained software designed to detect when they were undergoing official emissions testing and to alter engine performance accordingly to pass, while emitting far higher levels of nitrogen oxides under normal driving conditions.

Volkswagen subsequently admitted that roughly 11 million vehicles worldwide were fitted with the defeat device software, spanning multiple brands and model years. The admission triggered criminal investigations, tens of billions of dollars in fines and settlements, and the resignation of chief executive Martin Winterkorn within days of the EPA's notice.

“This was not a bug slipping through review; it was a feature, built to deceive, that shipped across eleven million vehicles.”

Software as an instrument of deception

What distinguished this case from a conventional mechanical defect was that the deception was coded deliberately: engineers wrote logic explicitly to recognise laboratory test conditions — steering position, speed patterns typical of dynamometer tests, duration — and to switch the engine into a lower-emissions mode only for the duration of the test.

This was not a bug or an unintended side effect; it was a functioning feature, built, reviewed and shipped across model years, that required the tacit or explicit cooperation of the software teams responsible for engine control units.

• EPA Notice of Violation issued 18 September 2015, followed by a matching notice from the California Air Resources Board.
• Approximately 11 million vehicles worldwide affected, according to Volkswagen's own admission.
• Cost to Volkswagen exceeded $30 billion in fines, buybacks and settlements in the years following disclosure.

A test case for professional conscience

The Volkswagen case became a touchstone in engineering ethics curricula precisely because it did not involve a rogue individual but an organisational structure in which no one apparently stopped the deception moving from design to millions of production vehicles. It raised uncomfortable questions about whistleblowing, chain-of-command pressure and the responsibility of individual engineers who write code they know is intended to mislead regulators and customers.

It also underscored that emissions compliance, like safety compliance, increasingly lives inside software rather than mechanical hardware — meaning the integrity of code, and of the people who write it, has become inseparable from environmental and public-health outcomes.

What the Society recommends

The Society treats the Volkswagen case as a clear illustration of why codes of ethics must have teeth and why individual engineers need protected channels to refuse or report unethical instructions.

• Uphold a professional obligation to refuse to build software designed to deceive regulators, auditors or the public.
• Establish and protect internal channels for engineers to raise ethical concerns without fear of retaliation.
• Treat compliance-critical software — emissions, safety, financial reporting — as subject to independent external audit.
• Recognise that a professional's signature or commit history carries accountability, and act accordingly.