Top 15 reasons why your engine management light is on

Cars are very good at self-diagnosing problems and recognising when vehicle components and parts aren’t working at 100%. Cars come with warning lights that usually appear on the dashboard and will turn on to let the driver know there may be an issue somewhere in the car. 

Most drivers dread warning lights; however, listening to them and swiftly acting on the warning to see what the problem is can help you better maintain your car. One of the most crucial warning lights you need to pay particular attention to is your engine management light. 

This light appears when there are issues with your engine. It’s always best to halt what you’re doing and check your engine when this light appears, as problems with this part of the car can become expensive if they’re not fixed quickly. 

The problem is that although having your engine warning light appear on your dashboard is a good indicator that something needs to be fixed with you’re vehicle, it can still be challenging to get an accurate diagnostics of the problem from the light alone. 

There can be a lot of different reasons why your engine light might appear, with them all varying in terms of severity and how difficult the fault will be to fix. That’s why whenever you see your engine management light appear, it’s best to get your car checked out by a mechanic to find the specific problem. Pay attention to your engine light, as not doing so could worsen the situation and cause engine failure. 

In this guide

What is the engine management light?

The specific engine management light is an LED light that appears on your dashboard. It’s usually symbolised by an engine icon and will temporarily light up orange when you start your ignition. If there’s an issue with your engine, this light will remain on once your car is fired up, indicating to the driver that you need to take action. 

Some cars may also have a separate ‘CHECK ENGINE’ light for a more obvious indication that something is severely wrong. The colour of your engine management light may also change to red on some vehicles to indicate a severe issue that shouldn’t be ignored.

It’s important to remember that the engine management light doesn’t indicate a specific fault as many of the other warning lights do. Instead, it’s there to alert you about one or more issues related to any car part within the engine system. 

Sensors dotted within your engine and exhaust system track various types of data and information. If the data they report to the car’s engine control unit (basically the car’s central computer) is wrong, the warning light will be triggered.

To help you understand what could be wrong with your car’s engine, here’s a list of 15 reasons why the engine warning light might appear on your dashboard.

Mass Airflow Sensor Issue 

An issue with your mass airflow sensor indicates that the quantity of oxygen coming into your engine isn’t at the proper levels. Thankfully, having a problem with your mass airflow has a low risk of damaging your engine. 

Instead, if you have too little oxygen coming into your engine, it will run poorly and likely idle and will not accelerate smoothly. Issues with your mass airflow could also impact your emission levels, although it may be hard to notice. 

You’ll likely have an issue with your mass airflow because of a blocked air filter. Make sure to replace this component and ensure that you change it for a new one after a couple of years.

Faulty Oxygen Sensor 

Your vehicle’s oxygen sensor measures the quantity of oxygen leaving your engine through the exhaust system. If the levels of oxygen are measured as being too low by the sensors, it will cause an engine management light to appear. 

There are at least two faulty oxygen sensors in modern cars, helping to ensure accurate readings. As both the mass airflow sensor and the oxygen sensor measure the oxygen levels in your car, if there’s an issue with one, there will also be an issue with the other. 

Thankfully, a faulty oxygen sensor only poses a low risk of damage, but you should still drive your vehicle to the nearest garage to inspect and repair it.

Faulty EGR Valve

ERG stands for exhaust gas recirculation, an essential process for ensuring that your engine runs smoothly and cleanly. This component diverts around 10-15% of the exhaust gas back into the engine where it is burned, helping to ensure that your car exhausts are clean. 

Over time, the ERG value responsible for this recirculation can get clogged up with carbon deposits, forcing the parts to stick either open or shut. This may result in rougher idling as your drive, engine misfiring, and difficulty starting the car. 

A sensor can sport if the valve is faulty and thus instigate an ECU light. Although there’s little risk for a faulty EGR valve to damage your car, you should still check it out so it can be cleaned or replaced.

Leaky Vacuum Hose

The vacuum hose of your engine is designed to suck up air and emissions within your engine to ensure it runs efficiently. These vacuums are exposed to massively high temperatures due to engine combustion and are usually made of plastic, which can deteriorate and crack over time. When this happens, the vacuums will be less effective at sucking up the gases in the engine, unsettling the balance of gases in this part.

Sensors can pick up this gas composition change, which alters the main ECU and triggers an engine management light. 

There’s little risk of your engine getting severely damaged when this happens, although you may find that you burn through more fuel than you should for your car’s model. 

Faulty Ignition System

The ignition system is a component that ensures that the air and fuel source in your engine is ignited correctly. Problems with your ignition system can cause engine misfires, which is terrible for your vehicle’s performance and has a high risk of damaging your catalytic converter. 

Petrol cars are more likely to have problems with the ignition system, and the most common parts that can cause ignition problems are the coils that make the spark used to ignite the fuel and the part that dictates the timing of the spark. 

As this issue can create other problems with more crucial parts, it’s best to drive slowly to a mechanic if you suspect that you have a faulty ignition system so that this problem can be fixed.

Blocked Fuel Injectors 

Fuel injectors squirt fuel into the engine, which is essential to ensure that your engine remains running. There’s one injector per cylinder of your engine, and the main car’s computer determines the timing of this injection. 

Fuel injectors can easily be clogged with wantaway particles that have made it through the fuel filter, which can impact the running of your engine and spark misfirings and a dramatic decrease in performance. 

Although fuel injector issues are primarily because of a clog, they can also have problems due to faults somewhere else in your engine system or fail after entering use. All of these will cause a check engine light, which shouldn’t be ignored. 

Blocked Fuel Pump 

The fuel pump is a part of the engine system that delivers fuel to the injectors and does so under very high pressure. Any issues with the fuel pump can mean that the injectors do not have enough fuel to squirt into the engine, which can harm performance and cause the engine to run really poorly. 

Your fuel pump can become blocked by particles that have made it through into your engine system, and if blocked, it will cause the engine light to appear. A lack of fuel can cause severe performance issues like misfiring or engine failure.

Most modern cars will revert to ‘limp home mode’, where the vehicle limits how much power is available to protect the engine. This allows you to drive the car to a mechanic without risking massive damage to your engine. 

Contaminated Catalytic Converter 

The catalytic converter is an integral part of the engine system used to clean up the car’s exhaust emissions, helping to reduce the amount of carbon produced by the vehicle. 

The catalytic converter can become damaged and even destroyed if it’s ignited by unburned fuel. Although you won’t experience many changes in your driving performance, you will have an increased emission output, which can be harmful if you need to stay under an emission limit, such as if you’re driving in a ULEZ zone. High emissions from a damaged catalytic converter may also mean that you fail your next MOT

If you think your catalytic converter is damaged, it’s best to drive slowly to your nearest mechanic to replace it. This can be an expensive piece of equipment, so don’t delay getting it fixed, as you may worsen the problem if you don’t.  

Sooty Particulate Filter 

The particulate filter is a part that is predominantly in diesel engine systems; however, it is also starting to appear in more modern petrol vehicles. This part is used to capture any soot created by the burning of fuel in your car’s engine and to stop this soot from getting into other parts of your engine system. 

Over time, this filter can get clogged with soot and other debris, triggering an engine management light on your dashboard. If you suspect that the engine light results from a sooty particulate filter, it may be worth increasing your engine speed to try and burn off the soot. 

If that doesn’t fix the issue, it’s best to get the problem resolved at a mechanic, as a particulate filter is a costly part to replace. 

Loose Filler Cap

A filler cap helps regulate the air coming into your engine. As fuel is pumped out of your engine’s petrol or diesel tank, air must be allowed in to replace it; otherwise, there will be a change in pressure which will impact the fuel flow. 

A loose cap may allow in more air than it should, which can create issues with the levels of fuel within your entire engine system. Thankfully, this issue is easy to fix by simply replacing the cap and has a low risk of damaging your engine.

Loose Oil Dipstick

Your dipstick is used to check the engine system’s oil level. If your engine management light turns on shortly after you’ve checked your oil, it may indicate that the dipstick is loose and has not been put back correctly. 

Although this seems like a trivial issue, a loose dipstick can rattle under your bonnet and cause damage or dislodge valves, caps, and other components in your vehicle.

Dead Battery

Your car battery is essential for your car to work. Without one, you won’t even be able to start your vehicle. This means that a dead battery can be catastrophic and will likely need to be replaced for you to continue driving your car. 

Most modern batteries last a reasonably long time and are designed to be easy to replace when the time comes. Although many cars will have their own battery warning light independent of the engine light, some might combine the two, so it’s worth checking the battery when you see an EML to make sure. 

Aftermarket Alarm Issues

If you’ve fitted an alarm system to your car, it can cause a whole host of issues to your vehicle if it’s not been fitted correctly. It can sometimes stop the car from starting, drain the battery, and even trigger a check engine light despite there being no problem with your engine. 

If an aftermarket alarm system is causing your engine light to appear due to electrical problems, you must get it fixed. This is because if it’s constantly arising for a faux fault, it won’t be able to light up if a genuine issue appears in your engine.

Faulty Spark Plug Wires 

Your spark plug wire transfers electricity from the coil to the spark plug. Without this electricity, you won’t be able to get an ignition in your engine. If these wires are damaged or become disconnected, your car will start failing to ignite, which can cause performance issues and misfiring, damaging other parts over time while also resulting in an EML.

Most cars have a single spark plug wire per cylinder, making them easier to find and fix, although some older cars have two per cylinder. A new set of wires can cost around £40, although replacing them is something you should be able to do yourself.

No Reason/Glitch

Sometimes your check engine light may appear on your dashboard despite there being no issues with your engine. There can be many reasons for this, with the most common culprit being electrical issues within your vehicle. 

Of course, whenever you get a check engine light, inspect it first to ensure that it isn’t an issue with your engine. Once you are confident that an electrical fault causes it, you’ll be able to reset the light manually. 

Engine Management Light FAQs

When an engine warning light appears on your dashboard, your vehicle will also generate error codes that indicate the specific issue with the car. You can decipher these codes with a code reader gadget, which plugs into your car's data port. 

Any individual can buy these code readers, making figuring out what's wrong with your engine much easier and less expensive. However, not all of these error codes will reveal a quick fix.

Primarily, these codes will indicate a symptom but not the cause of the issue. For example, you may get an error code that states a faulty sensor; however, it doesn't reveal why it's defective and how to fix it. 

This means that despite having this code-reading device, you'll also need mechanical knowledge of cars to fix the issue properly. 

When your EML appears on your dashboard, it may have different colours to indicate the severity of the issue within your engine. A solid amber light means that the problem is likely a minor issue, and although you may not need to stop immediately, it's still beneficial to check it out soon. 

A flashing amber light means that the problem is more serious, indicating the car is misfiring. The result is that the car will judder when driving and can also sound pretty rough. Continued driving can cause the engine to overheat, damaging your catalytic converter. When you see a flashing amber light, you should immediately drive it to a garage. 

A solid red engine management light will indicate a severe fault. When you see this, it's best to stop the car as soon as you can safely to prevent further damage. When you see this colour, you should call your breakdown recovery provider to have the car checked at the roadside, as driving it to a garage can cause more problems. 

Sometimes your check engine light will appear because of an electrical glitch, meaning that it's appearing on your dashboard despite there not being a genuine issue with your engine. If this happens to your car, it's best to try and reset it. 

Most of the time, you'll be able to reset an engine light by restarting your vehicle. However, if it's still there and you've checked that there are no issues with your engine, then you'll be able to reset it by plugging in an OBD, which stands for an onboard diagnostics tool. This will let you override the engine light and check for any error codes to ensure that there are no faults with your engine.

The colour of your check engine light will determine if you can drive when it's on. A solid amber light means it's a mild issue, and although you should get it inspected soon, you won't have to cut short your journey to go to a mechanic, and you should be able to drive normally. 

You may have to drive your car to a mechanic if you have a more severe issue. When doing this, it may be best to go slowly and use the accelerator as little as possible to help prevent more damage. 

If your vehicle shows a solid red warning light, it means there's critical damage to your engine, and you should stop driving the vehicle as soon as possible. To get the car fixed, you'll need roadside assistance, where the car will either be fixed on the roadside or towed to a garage.

Sometimes, when the engine management light turns on, your car may automatically revert to 'limp home mode'. This is where the vehicle limits how much power you can put into accelerating and driving. This protects the engine from getting more damage while allowing you to drive your car to a garage. 

If driving while under 'limp home mode', make sure to put on your hazards to alert other drivers that you're driving below the speed limit because of an issue. 

If your car automatically goes into 'limp home mode', the engine issue is likely severe and will require immediate fixing.

If your car goes in for an MOT while presenting an EML, it will be a major fault and cause you to fail your MOT. 

This is because if a fault is displayed, it would suggest that your car is either unsafe to drive or produces too many emissions than it should. That's why fixing any issues before your MOT is important to give it a better chance of passing. 

If you're trying to sell a car with an engine light on, you may find it harder to get an offer than you should for the car's model. Although you're not blocked from selling the vehicle, you will likely get much lower offers, especially if the buyer needs to know the reason for the engine light and how much it will cost to fix. 

When trading in a car as a part exchange, the value of the repair costs to clear the engine light will be priced into the offer. This means you'll lose out on how much you can get from the car. That's why it's best to clear any faults and issues before selling your vehicle to maximise how much you can get for it. 

Although all of the 15 reasons explored in the article are common, there is one issue that will most likely be your culprit and should be something you check before anything else. 

It's very common to have an oxygen sensor malfunction, which can mean that your car isn't expelling enough oxygen or that the sensor recording this data is broken. Fixing this issue by unblocking your air filter or getting a new sensor can help you quickly remove your check engine light. 

When your EML appears on your dashboard, it's always best to first check for any issues that are a quick and straightforward fix. This will allow you to either quickly check off any potential issues, or fix problems before driving the car to a garage. 

You should check to see that your filler cap isn't loose, as this can cause issues with your fuel levels within your engine and is easy to fix and replace. Although make sure that there are no problems with your electronics and that your dipstick is in the right place. 

It's also wise to check to see if the engine light wasn't prompted because of a glitch. Turn off your car and restart it to see if the light still appears. If it's not turned offer after these simple checks, then it's best to get it inspected by a mechanic at a garage.

A check engine light will eventually turn off on its own once the issue has been fixed. However, on some cars, it may not turn off immediately. This is because you may need to drive the car for around 50-100 miles for the sensors to gather new data and ensure that everything is working properly.

This means you shouldn't panic if you still see the engine light after getting an issue fixed at a garage, as it will likely disappear after a few miles of driving. That said, most mechanics will reset the alert anyway to ensure it's off once you leave the garage. 

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