Volkswagen installed software to cheat on emissions tests

In September 2015, the U.S. Environmental Protection Agency (EPA) discovered that Volkswagen had deliberately programmed diesel engines to produce false results during emissions testing. The software, installed in millions of vehicles sold between 2009 and 2015, detected when a car was undergoing a test and switched the engine to a low-emissions mode. Once testing ended, the engine returned to normal operation—which produced nitrogen oxide emissions up to 40 times higher than legal limits.

Volkswagen knew the engines could not meet U.S. emissions standards while maintaining the fuel efficiency and performance customers expected. Rather than redesign the engines, the company chose to deceive regulators and buyers. The scandal affected approximately 11 million vehicles worldwide, with roughly 500,000 sold in the United States.

The discovery triggered the largest automotive recall in U.S. history, criminal investigations in multiple countries, and a complete reshaping of how the company operated. Volkswagen's leadership faced prosecution, the company paid billions in fines and settlements, and the scandal became a turning point in how regulators monitored vehicle emissions.

Key Takeaways

  • Volkswagen programmed diesel engines with software that cheated on emissions tests by switching to a low-emissions mode only during testing.
  • The affected vehicles produced nitrogen oxide emissions far above legal limits during normal driving, harming air quality and public health.
  • The EPA discovered the deception through independent testing that showed a gap between lab results and real-world emissions.
  • Volkswagen recalled 11 million vehicles worldwide and paid over $15 billion in fines, settlements, and buyback programs in the United States alone.
  • The scandal led to criminal charges against company executives and prompted stricter emissions testing procedures across the automotive industry.

How the EPA discovered the cheating

The EPA did not find the software through routine inspections. Instead, researchers at West Virginia University were conducting a study on real-world emissions from diesel vehicles when they noticed something odd: Volkswagen diesels performed far better in the lab than on the road. The gap was too large to explain by normal variation.

The researchers reported their findings to the EPA in May 2014. The agency spent over a year investigating, asking Volkswagen repeatedly to explain the discrepancy. Volkswagen initially blamed the difference on testing procedures and driver behavior. In September 2015, after the EPA threatened to withhold approval for 2016 model year vehicles, Volkswagen admitted the truth: the company had installed defeat devices—software designed specifically to circumvent emissions standards.

What the software did and why it mattered

The defeat device operated through a straightforward logic: it monitored steering wheel position, vehicle speed, engine temperature, and barometric pressure to detect when a car was on a dynamometer (the treadmill-like machine used in emissions testing). When the software recognized these conditions, it activated a special emissions control mode that reduced nitrogen oxide output to legal levels.

Once the test ended, the software switched off this mode. During normal driving, the engines operated without the emissions controls, producing nitrogen oxide at levels the EPA found unacceptable. Nitrogen oxide contributes to smog and respiratory illness, particularly in children and people with asthma. The cheating meant millions of drivers were unknowingly contributing to air pollution far worse than they believed.

Volkswagen had made this choice deliberately. Internal documents later revealed that engineers knew the engines could not meet U.S. emissions standards without sacrificing fuel economy or performance—two features customers wanted and Volkswagen advertised. The company decided deception was cheaper than redesign.

The when ready response and recall

Volkswagen announced a recall on September 18, 2015, just days after admitting the deception. The company initially said it would fix the affected vehicles through software updates and hardware modifications, though the company did not when ready explain how it would reduce emissions without compromising performance or fuel economy.

The recall proved far more complicated than a typical fix. Volkswagen could not straightforward remove the defeat device—doing so would cause the vehicles to fail emissions standards. The company had to redesign engine components, which took months to develop and test. Some owners waited over a year for repairs. Others, frustrated by delays and skeptical that repairs would work, pursued buyback options.

By 2016, Volkswagen had begun offering to repurchase affected vehicles at fair market value, allowing owners to return their cars rather than wait for repairs. The buyback program eventually covered hundreds of thousands of vehicles in the United States.

Financial penalties and legal consequences

Volkswagen faced penalties from multiple directions. The EPA issued fines under the Clean Air Act. The Federal Trade Commission pursued charges for deceptive advertising. State attorneys general filed lawsuits. The company also faced criminal investigations in the United States, Germany, and other countries.

In the United States, Volkswagen agreed to pay $14.7 billion to settle civil and environmental claims—a figure that included $10 billion for the buyback and repair program, $2.7 billion for environmental mitigation, and $1.5 billion in civil penalties. The company also pleaded guilty to criminal charges, including conspiracy and obstruction of justice.

Individual executives faced prosecution. Volkswagen's CEO at the time of the scandal, Martin Winterkorn, was charged with fraud in Germany. Several engineers and managers received criminal sentences in the United States. The company's U.S. operations were placed under a court-appointed monitor to may support compliance with environmental laws.

How the scandal changed emissions testing

Before 2015, emissions testing relied almost entirely on controlled laboratory conditions. Regulators assumed that if a vehicle passed the lab test, it would meet standards on the road. The Volkswagen scandal exposed the flaw in this assumption.

The EPA and the National Highway Traffic Safety Administration (NHTSA) introduced new testing procedures called the Worldwide Harmonized Light Vehicle Test Procedure (WLTP). These tests include real-world driving conditions and are harder to game with software tricks. Regulators also began conducting more on-road testing to verify that vehicles perform as they do in the lab.

Manufacturers now face stricter oversight and more frequent audits. The scandal also prompted other countries to tighten their own emissions standards and testing methods. What had been a Volkswagen problem became an industry-wide wake-up call.

Long-term impact on Volkswagen and the industry

Volkswagen's reputation suffered severely. The company that had built its brand on engineering reliability and German precision became synonymous with corporate deception. Sales declined, particularly in the United States, and the scandal forced a complete leadership change.

The company responded by committing to electric vehicle development. Volkswagen announced plans to become a leader in EV manufacturing and began investing heavily in battery technology and electric models. Whether this strategy will restore consumer trust remains uncertain, but the company clearly recognized that its future depended on moving away from the diesel engines at the center of the scandal.

Other automakers faced increased scrutiny. Regulators investigated whether other companies had used similar defeat devices. Some manufacturers were found to have used legal but ethically questionable software that reduced emissions control effectiveness under certain driving conditions. The scandal created a permanent shift in how the industry approaches emissions compliance and how regulators monitor it.

Frequently Asked Questions

Which Volkswagen models were affected by the scandal?

Diesel-powered Volkswagen, Audi, and Porsche vehicles sold between 2009 and 2015 were affected. The most common models included the Volkswagen Jetta, Passat, Golf, and Beetle. Audi A3 and A6 models were also included. The scandal did not affect gasoline-powered vehicles or vehicles sold after 2015, though some 2016 models with carry-over engines were included in the recall.

Could owners have known their cars were cheating on emissions tests?

No. The defeat device operated invisibly to the driver. Owners had no way to detect the software or know that their vehicles were producing excessive emissions. Volkswagen advertised these cars as clean diesel vehicles that met environmental standards, which was false. Owners discovered the deception only when news of the scandal broke in September 2015.

What happened to owners who bought affected vehicles?

Owners had two main options: participate in the buyback program or have their vehicles repaired. Those who chose buyback received fair market value for their cars and could purchase a different vehicle. Those who kept their cars received free repairs, though the repairs took time and did not fully restore the original performance and fuel economy. Some owners also pursued class-action lawsuits seeking additional compensation.

Did other car manufacturers use similar defeat devices?

Volkswagen was the only manufacturer found to have used a deliberate defeat device as sophisticated as the one discovered in 2015. However, investigations found that other manufacturers had used software that reduced emissions control effectiveness under certain driving conditions. These practices were legal but ethically questionable, and they prompted regulators to close loopholes in emissions standards.

How did this scandal affect emissions standards globally?

The scandal prompted stricter testing procedures in the United States, Europe, and other regions. New tests include real-world driving conditions and on-road verification. Regulators also increased oversight and audit frequency. The scandal demonstrated that laboratory testing alone cannot may support compliance, leading to a fundamental shift in how emissions standards are enforced worldwide.