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Why Has My Engine Management Light Come On?

Published: 5 October 2022

Many people have seen their engine management light come on a few times and it could be for something very small and easily fixable and so often gets ignored. This light will appear on your dashboard behind your steering wheel either in the form of an engine block or the wording “check engine”. The warning light is the first sign that there is a potential issue in your car and annoyingly it does not tell you the exact problem as it could be triggered by several issues.

So, what can cause the engine management light to come on?

Here are some of the most common causes as to why your engine management light has been triggered.

  1. Loose oil dipstick

If you have recently checked your oil levels, then the engine management light could be triggered because the dipstick is loose. Double check the dipstick is back properly in the right position to see if that resolves the issue.

2. Loose petrol or diesel filler cap

If your fuel cap is loose you leave your car at risk of allowing in more air which can mess with the sensor that monitors the tank pressure. This is one of the simplest faults to cure, replace the cap and you will know if this is the cause of the engine management light being on.

3. Faulty oxygen sensors

Oxygen sensors measure the amount of unburnt oxygen going through the exhaust, indicating if the engine is burning too much or too little fuel. Another possibility could be the sensor itself has a fault; it is best to get this diagnosed by a professional to see what is happening.

4. Leaky vacuum hose

An engine has numerous vacuum hoses with various functions and due to them being constantly exposed to extreme temperatures they crack and fail, causing the engine management light to alert you to this issue.

5. Mass airflow sensor

There are a couple of systems to help identify if your mass airflow sensor is to blame, first of all, you may find it hard to start your car, and then when it does you may find that it stalls shortly thereafter. Your engine may "hiccup", jerking movements under acceleration need to be investigated at the earliest opportunity, whilst you can still probably drive your car under these conditions we recommend that you take it to a trusted, highly rated garage near you. 

6. Contaminated catalytic converter

This is responsible for cleaning the car’s exhaust emissions, turning harmful carbon monoxide into carbon dioxide. This converter can become clogged, especially if you are only always doing short journeys, if it does fail your car’s emission levels will increase causing the engine management light to be triggered.

7. Faulty ignition system

The ignition is responsible for ensuring the fuel and air are ignited correctly in the engine. In a petrol car, there could be issues with the spark plugs or if you drive a diesel vehicle, then your engine management light may linger whilst your glow plugs are warming up; if they're damaged it's likely you may see some white smoke. If left, this can lead to some more serious engine problems and so it is best to take it in as soon as you either feel the misfire or see the engine management light come on and stay on.

8. Blocked particulate filter

The particulate filter catches the soot created when fuel and air are burned in the engine, the engine management light will come on if the filter gets clogged. What may help if this is the cause is increasing the engine speed, making it hotter and burning off the soot. A damaged filter is expensive to replace so definitely get this seen too quickly to ensure no further damage.

9. Blocked fuel pump

This delivers fuel to the injectors under high pressure, any slight problem will upset the fuel and cause the engine to run badly. The engine management light will come on if it senses any issues here and could cause the engine to go into limp mode which effectively limits the amount of power available to protect the engine.

10. Faulty EGR Valve

This is the exhaust gas recirculation valve which controls the amount of nitrogen oxide in the car’s engine to help with the efficiency of the vehicle by redirecting some gases back through the cylinders. The valve can become stuck open or closed causing the engine to set off its alert light.

Can I drive my car with the engine management light on?

As the causes range from simple, easy fixes to more serious, expensive problems, how can you know whether it is safe to continue driving?

Well, most of the time if there are no obvious other signs of something being wrong with the vehicle you should be fine to continue driving to your destination. Once arrived you should then make sure you check your car over for any of the simple fixes and then get your car checked by an expert to ensure that you aren’t causing further damage and that it is still road safe. The engine management light in this instance might flash up yellow, orange, or amber meaning that there is an advisory to check your engine for a potential issue.

If you can see or feel other issues with the vehicle or the engine management light is flashing or red this may be an indicator that there is something more serious wrong with your car. Should this happen, you should switch off the engine and contact roadside assistance to help get your car to the nearest garage.

Will my car pass its MOT with an engine warning light on?

From 2018 onwards there have been stricter MOT rules, an engine management light will now mean an automatic fail. It’s worth checking whether there are warning lights on your dashboard before the MOT test to avoid failing. The engine management light will flash up quickly when you start the car, this is normal, it should then go out once the car is on if there are no issues to be checked.

What will happen if I ignore the check engine light?

Many people ignore the check engine light thinking it will be something small and non-terminal, but it's not worth the risk when it could be something more serious. Ignoring the light isn’t going to make any fault just go away, in fact, it might make whatever issue is causing the engine light to come on - to worsen, potentially ultimately causing your car’s engine to seize up, burn out and die. Don’t wait until this happens, it could be a quick and simple fix that a mechanic can easily diagnose, making the trip to the garage easy and inexpensive.

Don’t ignore your engine management light, get it checked by a professional, trusted and experienced garage near you.

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