Why Your Engine Warning Light Is On (And What To Do Next)

The engine management light can be activated by a whole host of issues. It can either be amber or red, depending on the severity of the problem and it’s vital not to ignore it. It doesn’t highlight specific faults, so it’s important to get the vehicle checked by a mechanic to diagnose and fix the problem. In this guide, we’ll be outlining some common causes, and what to do about it.

Types of Engine Warning Light

There are three types of engine management light (EML) to look out for:

• Steady (constant) amber
• Flashing amber
• Steady (constant) red

Having any type of engine warning light on your dashboard will result in an MOT fail as it is classed as a major fault. Here’s a quick summary of the three types of light and what to do if you see any of them on your car’s dashboard.

Why is the Engine Management Light On?

There are many different reasons why the engine warning light can become illuminated. It indicates a serious fault with the vehicle’s engine which can cause the car to breakdown suddenly. Here are some of the most common causes:

• Loose fuel cap
• Ignition issues e.g. faulty spark plugs
• Catalytic converter issues
• Blocked DPF filter
• Mass airflow failure (MAF) sensor issue
• EGR valve failure
• Fuel pump failure
• Weak or dead battery
• Transmission issues
• Loose oil dipstick
• Issues caused by aftermarket parts

Let’s take a look at each of these causes in a bit more detail.

Loose Fuel Cap

One of the most common causes of the engine management light switching on, is actually one of the simplest and quickest to fix. If you’ve just been to fuel up and noticed that an orange engine management light is now active, pull over safely and check that the fuel cap has been sealed properly. Pay attention when you try and seal up the fuel cap, if it looks worn and doesn’t click, then it may need replacing.

The reason that a loose fuel cap activates the engine warning light, is due to fuel vapours escaping the tank. Typically, these vapours are recirculated back into the tank, but any leaks (such as a loose fuel cap) will trigger the warning light.

If this is the cause, the engine warning light should only be a constant amber colour (not flashing) and will turn off relatively quickly after the fuel cap is properly sealed. If it stays on, get it checked by a mechanic as soon as possible.

Ignition Problems

Any issues with the spark plugs or ignition coils is likely to trigger the EML. This is a very common cause, and can result in either an amber or red light depending on the severity of the problem. Regularly servicing the car and replacing the spark plugs at the manufacturer’s specified intervals (usually around 3 years/ 30k miles) will prevent this issue in most cases.

Spark plugs are found in petrol engines and produce the spark which ignites the air-fuel mixture. A faulty spark plug will cause the engine to misfire. Again, it’s important to get the car to a mechanic as soon as possible even if the EML is a constant amber colour, as it can severely damage the catalytic converter if you continue to drive.

Catalytic Converter Issue

Leading on from the previous cause, another possible reason why the engine management light is on, is due to an issue with the catalytic converter. This issue can become expensive if it’s ignored, so getting the vehicle checked by a mechanic as soon as possible is vital (even if the light is a constant amber).

A catalytic converter controls the emissions produced by the car, and if becomes worn or clogged then it will trigger an amber EML. This can also be accompanied by a loss of power which causes the engine to feel restricted.

Blocked DPF Filter

On vehicle’s with a diesel engine, the diesel particulate filter (DPF) is used to capture and store soot to reduce emissions. The DPF can become blocked, particularly if the car is driven on short or slow journeys quite frequently.

A clogged DPF filter is a common EML cause, and often requires the attention of a mechanic. If the EML is a constant amber, it can be possible to regenerate the DPF by driving at a higher speed (40-70mph where appropriate), to maintain high engine revs, however if the issue persists after around 20-30 minutes then it’s important to get the vehicle checked. This issue is easily fixed if caught early, but if ignored then it can lead to costly repairs.

Mass Airflow Failure (MAF) Sensor Issue

Almost all petrol and diesel engines use MAF sensors which measure the amount of air entering the engine and help to maintain the air-fuel ratio. Several problems can cause the MAF sensor to trigger the engine warning light including a clogged air filter, cracked intake hose, or electrical faults with the sensor itself. In most cases, this will result in a steady amber EML.

EGR Valve Failure

The exhaust gas recirculation (EGR) valve is important to control the emissions produced by the vehicle. If it gets stuck or clogged, then the engine can’t control the emissions produced and will trigger an EML (usually steady amber). This issue is also usually coupled with engine shaking, loss of power and sometimes black exhaust smoke. It makes the car very unreliable and can lead to more expensive issues if left unattended.

Fuel Pump Failure

The fuel pump is used to transport fuel from the tank to the engine. Any issues with the fuel pump can trigger an amber EML as it means the engine is not receiving enough fuel. This issue is also typically accompanied by difficulty turning over, frequent stalling and loss of power.

Weak or Dead Battery

If the battery is weak, then it won’t be capable of holding a charge and can trigger the EML. Most car batteries need replacing every 3-5 years on average. If you’re having difficulty turning over, or having issues with your car’s stop/ start system combined with an amber EML, then it’s likely this is the issue and that the battery needs replacing.

Transmission Issue

Although not the most common cause of an EML, issues with the car’s transmission can sometimes trigger it. This will also typically be accompanied by a transmission warning light (a cog icon with an exclamation point inside). Some common issues could be slipping gears or low transmission fluid. If you notice both the EML and transmission warning light, tell your mechanic and get the vehicle checked immediately.

Loose Oil Dipstick

Another possible cause of an EML and thankfully one that is also quick to fix, is a loose oil dipstick. If you notice an amber warning light after changing the engine oil, check that the dipstick is seated properly. If it’s not, then it can affect the air-fuel mixture and trigger the EML. Make sure you also re-check the oil level if you notice the dipstick was loose, as some may have splashed out.

Issues Caused by Aftermarket Parts

If your car is modified with aftermarket parts or has been remapped, this can sometimes trigger the EML. This may be due to incorrect installation, or incompatibility with the vehicle, and can interfere with the engine control unit (ECU) and cause the EML to activate.

There are a whole host of reasons this can happen, but most often it’s due to one of the following:

• EGR or DPF deletes
• Exhaust modifications
• Air intake modifications

What to do when the Engine Management Light is on?

If you notice the engine warning light is illuminated on your dashboard, then it’s important to get the vehicle checked as soon as possible.

• If the light is a constant (steady) amber – book a diagnostic check at your local garage straight away
• If the light is either flashing amber or red – do not drive the car and get it recovered to your local garage

The mechanic will do a diagnostic check on the vehicle by connecting a scanner to the on-board diagnostics port. This will allow them to diagnose the issue and how to fix it. In most modern vehicles, the EML will reset as soon as the issue has been resolved.

Get Your Engine Warning Light Checked in Worcester

Here at Recharged Automotive in Worcester, we have over 30 years of experience fixing cars so you can rest assured that your vehicle is in good hands. Our highly-trained technicians can work on petrol, diesel and electric vehicles, and we pride ourselves on our commitment to providing excellent customer service. If you notice an EML, get in touch by calling 01905 458156.