Will My Car Fail an MOT with an Engine Management Light On?

Understanding the Engine Management Light (EML) and MOT

The Engine Management Light (EML), also known as the check engine light, is a critical indicator on your car’s dashboard. It illuminates when the vehicle’s sensors detect potential issues with the engine or emissions system. Understanding its implications for your car’s MOT test is essential for every driver.

1. The Significance of the EML in MOT Testing

A continuously illuminated EML is classified as a major fault during an MOT test, leading to an MOT failure. The EML can signal a variety of issues, ranging from minor to severe, but its presence indicates that the vehicle may not be operating as cleanly or safely as required. The severity of the problem can vary, but an illuminated EML generally means there is a significant issue that needs addressing​​​​​​.

2. Different Colour Codes of the EML

  • Amber Light: A steady amber light is usually advisory, indicating a problem with the engine’s performance. While it might not be an emergency, it’s advisable to get the car checked by a mechanic.
  • Red Light: A red engine light is more serious. If this light is illuminated, you should stop driving and arrange for your vehicle to be towed to a garage as it may indicate a severe issue, potentially leading to expensive damage​​.

3. Common Causes of the EML Being Triggered

  • Emissions system fault
  • Blocked diesel particulate filter
  • Differential pressure sensor fault
  • Mass airflow sensor issue
  • Ignition system fault
  • Loose petrol or diesel cap

These are just a few examples of what might trigger the EML. Sometimes, the light may illuminate due to temporary issues like changes in humidity, which can cause it to turn off eventually. However, it is crucial to identify and address the underlying issue promptly​​.

4. Taking Action Before the MOT Test

Since MOT regulations became stricter in 2018, any illuminated engine light, whether amber or red, results in an automatic fail. Therefore, if the engine light is on, it’s essential to have your vehicle checked and repaired by a skilled mechanic before undergoing the MOT test. Remember, it’s normal for the engine light to light up before starting the car, but if it remains on while the car is running, it indicates a problem that needs attention​​.


An illuminated Engine Management Light is a clear indication that something is not right with your vehicle. Not only does it lead to an MOT failure, but it also signals potential issues that could affect the safety and performance of your car. Addressing these issues promptly not only ensures a successful MOT test but also contributes to the overall health and longevity of your vehicle.