Engine Management Light: Why Has It Come On?

Engine Management Light: Why has it come on? in white letters over an image of a check engine light

An engine management light is one of the worst warning lights to see. What does it mean? Is the problem serious? How much is it going to cost to repair the damage?

If you’re stressing over an engine management light, we’re here to help!

We’re going to cover what your engine management light means, what you should look out for, some potential causes and, most importantly, what you should do about it.

So, what is the engine management light?

 

This article should answer all your questions but, if there’s something we’ve missed, drop us a comment and we’ll do our best to fill you in! There are no silly questions, so feel free to ask away!

 

What does my engine management light do?

It alerts you to problems with your car. It’s connected to the Engine Control Unit (you car’s brain), and translates mechanical issues into a single warning light.

As this can mean anything from a misfire to a sensor issue, it doesn’t always make life easy for you. We’ll explain why in a minute.

 

What does my engine management light look like?

It looks like this:

 

amber engine management light

 

It can also show as the words ‘check engine‘. The colour of the warning light is the most important factor.

So, what does that amber mean? Well, a solid amber engine management light is good news (in a very loose sense of the phrase).

It means that, while your car has a problem, you can still drive semi-normally. You should nurse the car home and get the problem sorted as soon as possible – but if you can’t book an appointment for a few days, you can still use the car. Just be sensible with it.

A flashing amber light makes driving slightly more risky. This is a more concrete sign that your engine isn’t running smoothly. As such, you shouldn’t drive with a flashing amber light. Find somewhere safe to pull over and call your recovery provider. Get them to tow you to the nearest garage to be safe.

The red engine management light is the most severe. You MUST stop driving if you see this as your engine has a critical fault. Pull over safely and get your recovery provider to take you straight to a garage.

At any point, your car could enter ‘limp home mode’. This limits your speed, slowing you to a crawl and doing just enough to get you home. Symptoms of ‘limp home mode’ include:

  • Sluggish acceleration
  • A top speed somewhere between 35 and 45 mph
  • RPM limited to less than 3,000
  • An illuminated engine management light

Your engine usually activates ‘limp home mode’ when it detects a very serious problem. It’s a failsafe built in to stop the engine from switching off altogether – so never ignore it.

In fact, you should never ignore the engine management light. It doesn’t come on for no reason. You should always take it seriously and prioritise safety over convenience, especially if it’s red. It means there is a problem which needs looking at.

But what sort of problem could it be?

 

What caused my engine management light to come on?

There are far too many potential reasons why you’re seeing this warning light to cover in one article. We’ve listed some of the most common below, but this is no exhaustive list. Anything that disrupts the balance of driving and isn’t linked to a specific part can trigger the warning light.

 

Having trouble telling one warning light from another? Let us give you a hand!

Loose Fuel Filler Cap

If your engine management light comes on after filling up at the pump, there may be a simple solution.

Your fuel chamber needs to be fully compressed in order for it to work properly. That rushing sound when you take the cap off? That’s the pressure escaping.

Your ECU knows when your fuel tank isn’t completely sealed and activates the engine management light. Always check that you’ve screwed the filler cap on tightly when you finish filling up.

If the light comes on and you’ve tightened the cap properly, you might need a replacement fuel filler cap. These are easy to find and only cost around £10.

 

Ignition System Fault

There’s a lot more to the ignition system than just turning a key. Carbuyer offers a great explanation of how the ignition system works, but here’s the simplified version.

Spark plugs provide the spark that causes combustion between the fuel and air in the engine. If they develop a fault, your car can’t complete the combustion process and you’ll experience problems with the ignition system.

If you notice dips in power and an occasionally jerky drive (as well as a warning light that fluctuates between amber and flashing amber), you might need new spark plugs, spark plug leads or coils and/or a new distributor cap.

These parts cost around £150 in total, but if you’re experiencing incomplete combustion and an engine management light, it’s a price worth paying.

 

driver looking under the bonnet at smoking, overheating car engine
Chances are, your car will give you a warning long before your engine overheats – so don’t ignore your engine management light!

 

Emissions System Fault

The Euro 6 regulation forces cars to be as environmentally friendly as possible. Exhaust fumes affect the air quality because of the noxious gases combustion produces. To limit polluting gases while maintaining the right level of driveability, manufacturers have had to redesign their exhaust systems.
 
This redesign means including at least one oxygen sensor in every exhaust manifold.

These sensors monitor the oxygen content of exhaust fumes and report back to the ECU. If too much or too little oxygen leaves the exhaust, it will trigger the engine management light. Burning too much fuel and not enough air during combustion means the engine is running too ‘rich’. The mixture should be fairly even at all times.

A fault in the sensor itself can also trigger the engine management light. If the ECU can’t measure something accurately, it might initiate ‘limp home mode’. It always errs on the side of caution by assuming there is a severe problem because it doesn’t have the data to tell it otherwise.

 

Mass Airflow Sensor Fault

This is another monitoring tool, designed to keep the mixture of fuel and air burned as even as possible.

Again, the engine may enter ‘limp home mode’ if the mass airflow sensor fails. If there is no data about how much air the combustion is burning, it assumes the engine isn’t getting any. This guards against overheating or expensive engine damage.

You may experience rough idling or jerky acceleration if your engine isn’t burning enough oxygen during the combustion process.

 

Blocked Fuel Pump or Fuel Injectors

Similarly, you may see the engine management light if your engine isn’t burning enough fuel during combustion.

You might notice misfires and poor engine performance if gunk or other particles are blocking your fuel injector, or the pump isn’t providing the injectors with enough fuel. Once again, the engine may also go into ‘limp home mode’.

 

Remember, these are just the most common causes. There are a wide range of problems which could trigger the engine management light, so it’s a difficult problem to get on top of.

 

What should I do about it?

You need to get the problem fixed.

That’s a very simplistic view of a complicated process. It’s hard to know exactly what your problem is without the right equipment. This usually takes the form of an OBD-II diagnostic scanner.

These are easy to find and only cost between £35 and £70 – but they’re not a magic wand.

The scanner may find the problem but it can’t fix the problem on its own. That’s why they’re used by professional mechanics as part of a diagnostic check.

 

diagnostic scanner in use by mechanic to find cause of engine management light

 

For the same price as an OBD-II scanner, you can book a diagnostic check at one of our 9,000 UK garages and have a professional mechanic find the problem for you! Once they find the problem, they’ll be able to give you an accurate repair quote, fix the problem and reset your engine management light.

Any details you can give them about the problem make their lives a lot easier, but that doesn’t mean you need to invest in a scanner. Telling them why your car feels wrong to drive is always a good starting point that they can expand on with you. If they get a good picture of the problem early, it helps make the diagnostic check even quicker!

And, as with any car problems, it’s worth acting sooner rather than later.

 

Book a diagnostic check today to find out why your engine management light is on!

 

Why should I do something about it?

If you’re not experiencing poor performance even though the engine management light is on, you might be wondering whether it’s worth booking a diagnostic check at all.

For starters, you don’t know why you’re seeing this warning light. There’s always a reason for it and, while it might not seem like a big deal right now, it could soon turn into one. One problem can lead to another and then, all of a sudden, you’ve got an expensive repair bill on your hands.

Finding the problem early is always best.

Most importantly, an engine management light is an automatic MOT failure.

This is a fairly recent development as the Ministry of Transport changed the MOT test in 2018. Faults are now categorised as minor, advisories or major in an effort to clamp down on unroadworthy vehicles. An engine management light, in any form, is a major fault and an automatic fail.

So you have to deal with it at some point. Why not remove some of the stress of an MOT failure and make it sooner rather than later? Book a diagnostic check with Book My Garage today!

 

Recap

Your engine management light can come on for many different reasons and you should never ignore it. What’s more, you should always remember:

  1. A red engine management light means that you need to stop your car immediately, when it is safe to do so
  2. An illuminated engine management light causes an MOT failure
  3. The only way to reset the warning light is to fix the problem with a diagnostic check
Mandy Weston

Mandy Weston

Mandy is an ex-mechanic, with 22 years’ experience in the motor industry. As an in-house motoring expert, Mandy is the go-to woman for any relevant questions that our customers have; both garages and drivers. From specific problems with your car to general maintenance, Mandy is a reliable source of information and advice. Her passion for motoring is a huge factor to her success and the huge wealth of knowledge that she has. She now uses her remarkable grasp of the industry to write regular content for our readers to help drivers understand their car better, avoid being ripped off by garages and save money on their motoring requirements.

2 Replies to “Engine Management Light: Why Has It Come On?”

  1. My car (Toyota vitz)engine check light comes on after driving continuously above 100 kph for more than 20‐30 minutes. Furthermore, there is sudden (not gradual) deceleration after lifting feet off the accelerator.

    1. Mandy Weston Mandy Weston says: Reply

      Hi Tariq,

      I am sorry you are having such a difficult issue with your car. An Engine Management light indicates a fault in the engine, and I am afraid it doesn’t get any more specific than that. There could be a problem with one of hundreds of components, so you need specialist diagnosis using a computer that would read the fault. I would suggest you visit our comparison site and select a garage near you using your post code and registration number and select the diagnostic check option, you will then get the opportunity to type in the symptoms and book a day that suits you. The garage can then carry out a full diagnostic test and let you know the cause of the fault and the cost to remedy.

      Good luck, and if you wanted to talk to us again after the diagnosis with any other questions let us know.

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