Having the engine management light appear can be concerning, but what does this light actually mean, how serious is it, and what can you do to sort it?
An engine management light, or EML (sometimes also called the ‘check engine light’) is a dashboard warning light that illuminates when an issue with your car’s engine, exhaust or emissions system has cropped up. The EML will not alert you to a specific issue as a ‘low coolant’ or ‘check oil level’ message or light would, instead being a general warning that there is something wrong with your car.
What is the engine management light?
Modern cars feature multiple on-board sensors that monitor how the engine and other systems are performing. By measuring things like the amount of air being drawn into the system, the type of emissions being produced, how well the engine is igniting the fuel, and numerous other aspects, a car’s on-board computers can tell how well the vehicle is running.
When something goes wrong – either slightly or seriously – the EML can illuminate to alert you. The EML is represented by a universal symbol in the shape of an engine outline, while each car can show an amber, red or flashing EML, with each indicating a certain severity of problem.
What does the engine management light mean?
Amber engine management light
An orange or amber light is the least serious. If this light comes on and persists, it means that you should be able to keep driving as normal, but take your car to be looked at by a garage as soon as you can.
Flashing engine management light
A flashing orange light means that there is a problem that could affect how the car drives or handles, such as an engine misfire. You might be able to feel your car shake, or the engine could suddenly sound different. If this light comes on, you should take your car to be inspected immediately.
Red engine management light
A red engine management light means that there is a very serious problem. If you see this, you should stop at the nearest safe place and call your breakdown provider straight away.
What to do if the engine management light comes on
As outlined above, what you do if the EML appears will to a certain extend be determined by what type of EML is showing, but in short you should get your car looked at as soon as possible, stopping driving if the red EML appears, or you have any concern that your car may lose power or stop altogether – you don’t want to be on the road when either of those things happen.
What can cause the engine management light to come on?
Here are some of the most common problems that could cause your engine management light to turn on:
Oxygen sensors/mass airflow sensor
Oxygen sensors measure how much unburnt oxygen passes through the exhaust. This indicates whether or not an engine is burning too little or too much fuel and, if the sensors find a problem, they can set off the engine management light. Mass airflow sensors (MAF), meanwhile, measure the fuel/air mixture in an engine, and if they detect this blend is not right, of if a MAF develops a fault itself, the EML light can appear.
If you’re in a petrol car, problems with your spark plugs can set off your engine warning light. Replacing one or more spark plugs should fix this issue, although the problem may be to do with something else, including coil packs, which control the spark plugs.
Loose fuel cap
If your fuel filler cap is loose or missing, it can set off your engine management light. This is because a loose cap can cause vapour loss, where fuel evaporates and subsequently escapes from the car. This reduces your fuel efficiency and can also be a safety risk.
Luckily, a loose fuel cap is an easy fix. Just reattach it properly and the engine management light should turn after you’ve been on the road for a short while.
Blocked fuel pump
Over time, it’s easy for a fuel pump to become clogged or dirty, to the point where it doesn’t do its job properly. This is a serious issue, with the potential to not only turn the engine management light on, but also briefly cut the engine when you’re driving at high speeds.
Damaged catalytic converter
The catalytic converter is responsible for reducing harmful emissions made by your car. It transforms toxic carbon monoxide and nitrogen oxide gases into a mix of CO2, nitrogen and water. Problems like unburned fuel leaking and/or a leaky exhaust valve can damage or even break your catalytic converter, which will subsequently activate your engine management light.
A damaged catalytic converter is a major problem, proving environmentally unsafe and potentially expensive. If this happens, take your car to be serviced as soon as you can.
Blocked diesel particulate filter
A diesel particulate filter (DPF) is fitted to modern diesel-powered cars in order to trap soot from the exhaust and reduce your emissions. DPFs need to clean, or ‘regenerate’ themselves periodically, and this tends to occur when the car is driven at higher speeds (above 40mph or so) for a reasonable period of time.
If the DPF doesn’t regenerate when it needs to, it can become blocked and subsequently cause your engine management light to turn on. You may be able to get the DPF to regenerate by driving at a higher speed (where limits allow) or by maintaining high engine revs, but in other cases you may require the attention of a mechanic. Cars with a DPF tend to have a dedicated warning light to indicate the filter is blocked, but the EML light is likely to appear as well. Our guide to DPFs has more details.
How to reset the engine management light
As sophisticated as they may be, modern cars can develop glitches, and it’s possible turning the engine on and off may be enough for the EML to disappear.
This is, unfortunately, not always the case, and even if the EML disappears on startup, it may reappear as you drive on.
If the cause of the issue was simple (EG a loose fuel cap) then putting this right and restarting the car may resolve issues, either immediately or after a short while of driving. If the light doesn’t go out after you’ve fixed the issue you will need to have it reset, though, and this will require plugging in an OBD (on-board diagnostics) tool – which is probably a good idea anyway, as the technician with this will be able to scan for any error codes that might be present – it’s possible for more than one thing to go wrong at a time, after all.
You could consider disconnecting the negative lead from the car’s battery to reset the EML, but this can cause other issues to appear, so it’s best to do this only if you’re confident in what you’re doing.
Is an engine management light an MOT failure?
If your engine management light comes or remains on during an MOT, then it is classed as a major fault. After all, if the light is on, there’s a very good chance your car is either unsafe or nowhere near as clean as it should be.
Long story short: an illuminated engine management light is an instant MOT fail.
Engine management light on and loss of power
If your car’s on-board brain has detected a very serious problem, then not only will your engine management light go off; your car will likely enter limp mode, too. This is a failsafe fitted into most cars to try and stop your engine and/or gearbox from totally packing in as you’re driving.
It should be easy to tell when your car has entered Limp Home Mode. Not only will the engine management light be illuminated, but you’ll also notice considerable changes in how your car feels on the road. Acceleration will be more sluggish, your top speed may be limited, and your engine will be restricted to less than 3,000 revs per minute.
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If you’ve recently had an EML appear on your old car (or perhaps you just fancy a change), head over to carwow to browse our latest offers from our trusted dealers.
And if you’ve got a car you’d like to move on (though the EML light will need not to be showing!), our Sell My Car service is a great way to find it a new home – simply upload a few photos, enter some basic details and dealers will bid on it, leaving you to pick the best offer, and receiving payment when the dealer comes to collect the car.