# defeat device

> software

**Wikidata**: [Q21041527](https://www.wikidata.org/wiki/Q21041527)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Defeat_device)  
**Source**: https://4ort.xyz/entity/defeat-device

## Summary  
A defeat device is software designed to circumvent vehicle emissions regulations by detecting when a car is being tested and temporarily reducing pollution levels. It gained widespread public attention during the Volkswagen emissions scandal in 2015. These tools are considered fraudulent because they allow vehicles to emit more pollutants during normal driving than during regulatory testing.

## Key Facts  
- Used primarily in the context of vehicle emissions control systems  
- Classified as both software and a form of fraud  
- Also known by the Dutch term *Sjoemelsoftware*  
- Instance of: computer hardware, software, physical tool  
- Main subject: vehicle emissions control  
- Related class: computer hardware (physical components of computers)  
- Sitelink count: 8 across multiple language Wikipedias  
- Google Knowledge Graph ID: /g/11ckr3sfjg  
- Microsoft Academic ID (discontinued): 2780949784  
- Featured in: WikiProject Climate change  

## FAQs  
### Q: What is a defeat device used for?  
A: A defeat device is used to manipulate vehicle emissions tests by activating pollution controls only during testing. In real-world driving conditions, these devices disable or reduce the effectiveness of emissions controls, allowing higher pollutant output.

### Q: Is a defeat device legal?  
A: No, defeat devices are illegal under emissions regulations in many jurisdictions, including the United States and European Union. Their use constitutes fraud and can lead to significant fines and penalties for manufacturers.

### Q: How was the defeat device discovered in Volkswagen vehicles?  
A: The defeat device in Volkswagen diesel cars was uncovered in 2015 by researchers from West Virginia University working with the International Council on Clean Transportation. They found that VW vehicles emitted up to 40 times the legally allowable nitrogen oxide levels during regular operation compared to lab tests.

## Why It Matters  
Defeat devices undermine environmental protection efforts by enabling automakers to bypass emissions standards without consumers' knowledge. This deception has major implications for air quality, public health, and climate change mitigation. The discovery of such devices sparked global regulatory crackdowns, massive recalls, and billions in fines. Beyond legal consequences, it eroded trust in automotive industry claims about clean technology and highlighted weaknesses in emissions testing protocols worldwide.

## Notable For  
- Association with the 2015 Volkswagen emissions scandal  
- Being classified as both software and a physical tool  
- Use of deceptive programming to cheat environmental compliance tests  
- Triggering international investigations into automotive emissions practices  
- Highlighting gaps between laboratory testing and real-world performance  

## Body  

### Definition and Functionality  
A defeat device is software embedded within a vehicle's engine control unit (ECU). Its purpose is to detect standardized test conditions—such as consistent speed, temperature, and steering behavior—and activate full emissions controls only during those periods. Outside of testing environments, the device reduces or disables these controls, leading to significantly increased emissions.

### Legal and Regulatory Status  
The use of defeat devices violates emissions laws in numerous countries. In the U.S., the Clean Air Act prohibits any mechanism that bypasses or defeats emission control systems. Similar prohibitions exist in the EU under Regulation (EC) No 715/2007. Despite this, several automakers have been caught using them, resulting in lawsuits, recalls, and financial penalties exceeding tens of billions of dollars globally.

### Historical Context – The Volkswagen Scandal  
In September 2015, the U.S. Environmental Protection Agency (EPA) revealed that Volkswagen had installed defeat devices in approximately 11 million diesel vehicles worldwide. These vehicles falsely reported low emissions during tests but released harmful nitrogen oxides at rates far above legal limits while driven normally. The scandal led to criminal charges, executive resignations, and sweeping changes in how regulators approach emissions verification.

### Technical Classifications  
According to Wikidata and academic sources:
- **Instance Of**: Computer hardware, software, physical tool
- **Main Subject**: Vehicle emissions control
- **Aliases**: Sjoemelsoftware (Dutch)
- **Use**: Fraudulent manipulation of emissions data

### Multilingual Coverage  
The concept is documented across eight Wikipedia languages: German, English, French, Italian, Japanese, Korean, Dutch, and Chinese, reflecting its global relevance in discussions around automotive regulation and environmental policy.