Engine management light

Why is my engine management light on?

And what you should do about it

Has your vehicle’s engine management light (EML) turned on? It normally takes the form of an engine block or “check engine” wording and appears on the dashboard behind your steering wheel.

A dashboard warning light can often be one of the first signs of a problem with your vehicle. The EML is generally triggered when your car’s sensors detect a potential issue with the engine.

But how do you know exactly what’s causing the EML to come on and what can you do about it?

Below, we outline some of the causes of the engine management light and what you can do to resolve the issue to continue driving safely.

Read our complete guide to dashboard warning lights and what they mean.

In this article

Engine management light lit up on car dashboard

What does the engine management light mean?

The EML or check engine light is a bit different to other dashboard warning lights. This is because it doesn’t alert you to a specific fault.

A flashing or continuous EML lets you know there might be a problem with the engine. There are a number of reasons that can cause this, ranging from minor issues to much more serious ones.

Cars have sensors to check everything is running smoothly – if an issue is found relating to exhaust emissions, the sensor will tell the engine control unit (ECU) which turns on the EML. A broken sensor can also turn on the EML.

Is it safe to drive with the engine management light on?

Generally, unless there are other symptoms that’s something’s wrong, you can continue driving to your destination. You should then get your vehicle looked at by an expert as soon as possible to avoid risking further damage to your car.

But if you experience other issues with your vehicle that suggests something’s wrong with the engine, or the EML is red or flashing while the engine is on, this could indicate a more serious problem. If this happens, you should:

  1. Pull over as soon as it’s safe to do so.
  2. Switch off the engine.
  3. Contact us to report your breakdown so one of our patrols can help diagnose and resolve the problem.

We provide 24/7 roadside assistance.

How do I fix a car engine management light?

There are several problems that may cause an EML to switch on and diagnostic equipment is required to find it. You’ll need to get a mechanic to find and fix the issue so you should take it to a garage as soon as possible.

But if you’re experiencing other issues with your vehicle that indicate an engine problem, or the EML is red or flashing while driving, this suggests a more serious fault so you should stop driving as soon as it’s safe to do so and contact us to report your breakdown.

What can cause the engine management light to come on?

There are many reasons your EML might turn on. Some of the most common are listed below.

1. Oxygen sensor malfunction

If the sensor detects issues that your vehicle’s fuel is too rich (not enough air) or too lean (too much air, the EML might turn on.

It may also be illuminated if there's a fault with the sensor.

2. Blocked diesel particulate filter

The diesel particulate filter (DPF) captures and stores exhaust soot to help your engine pollute less.

If there’s a fault with it or the differential pressure sensor, which lets your car know the status of the DPF, the EML light might come on.

3. Mass airflow sensor

The ECU relies on the mass airflow sensor to work out how much fuel to add to the combustion chambers to correlate the amount of air coming into the engine.

If the air filter is missing, damaged or blocked, this can cause the EML to come on.

4. Ignition system fault

If you have a petrol car, problems with your spark plugs or coils may cause the EML to come on.

5. Loose oil dipstick

If the EML turns on shortly after you’ve checked the oil in your car, it could be due to the dipstick being loose. Make sure the dipstick has been put back properly and see if that resolves the issue.

Can low oil cause the engine management light to come on?

If your car's low on oil, this is a serious issue that should be resolved as soon as possible. But it very rarely results in the EML switching on.

Low oil has its own dashboard warning light (it usually looks like an oil can) that should alert you to this issue.

Find out how to check and top up your oil.

We'll help you get back on the road.

Will a car’s engine management light reset itself?

No, if the EML comes on in your car, you’ll need to take it to a garage so that a mechanic can diagnose and fix the fault. After the issue has been resolved, the light will turn off automatically.

If the EML turns on again, after the problem is fixed, you should take your car back to the garage.

You might find that when the EML first turns on, it turns off again after a short while. If it turns off and on intermittently, this is due to the fault only being detected by the sensor at certain times. You should take you car to a garage to resolve the issue and stop the EML turning back on.

Does an engine management light fail an MOT?

An amber or red EML that stays on when the engine has been started is classed as a major fault. This means it will cause your vehicle to fail its MOT test.

Use our MOT checklist to help pass your next MOT test.

More on car issues:

Published: 8 December 2021 | Updated: 8 December 2021 | Author: The AA

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