Engine Management Light: 25 Common Reasons Why It Comes On!
Is your engine management light blinking at you? You’re not alone! There are literally hundreds of issues why the engine management light might come on. However, to help you out, we’ve narrowed it down to the most common causes.
If you want to avoid automatic MOT failure, learn what’s wrong with your car and fix the underlying issue immediately.
So, without any further ado, let’s get started!
What Does Engine Management Light Mean? What are its Different Types?
The Engine Management Light (EML) is a warning indicator on your vehicle’s dashboard. It serves as a communication line between your car and you. There are many different names for an engine management light. Sometimes, it is referred to as a check engine light or engine warning light.
The EML is part of the vehicle’s onboard diagnostics system, continuously monitoring various engine parameters. When it detects an anomaly, it triggers the light to alert you.
Many issues can cause the EML to come on. This could range from something as simple as a loose fuel cap to more complex problems like emissions system failures. Different vehicles may use different symbols for the EML, but its function remains the same across makes and models.
Understanding the EML is essential for every driver. Ignoring this warning can lead to severe consequences, including reduced performance and costly repairs.
The Engine Management Light has three different types. Each type indicates a different level of concern. Let’s understand each type of EML:
1. Steady Amber Engine Management Light
This is the most common scenario you might encounter. A steady amber light typically indicates a minor issue, often related to the emissions system or fuel efficiency. While you may continue driving under these circumstances, it’s advisable to get your vehicle checked by a mechanic soon. Ignoring this light could lead to more significant problems down the line.
2. Amber Engine Management Light Flashing
A flashing light is more serious and should not be ignored. It indicates a critical problem that could damage your engine or catalytic converter if you continue driving. In this case, you should stop your vehicle immediately and seek professional help. Continuing to drive with a flashing EML can lead to severe engine damage and costly repairs.
3. Steady Red Engine Management Light
This is the most alarming signal you can see on your dashboard. A steady red light indicates a severe fault that requires immediate attention. It could mean your engine is overheating, or there’s a significant oil pressure issue. If you see this light, stop driving as soon as it’s safe and contact roadside assistance or a mechanic right away.
Top 25 Reasons Why an Engine Management Light Might Come On
Before we dwell on the specific reasons, remember that the EML is a broad indicator, not a specific diagnosis. It simply signals that the vehicle’s ECU has detected a problem within the systems.
There are no less than 100 issues due to which an engine management light can come on in modern vehicles. So, you can never be sure why an EML might have lit up. Therefore, to be sure, you must always look for other symptoms in conjunction with the engine management light.
For instance, an issue with the transmission system can cause the EML to light up. But it doesn’t tell you what’s exactly wrong with the transmission system. It can be a sensor-related issue or a simple transmission fluid leak. So, you should always be attentive to other symptoms such as unusual noises, changes in performance, or fluid leaks.
These additional indicators can provide valuable context that aids in diagnosing the problem more accurately. Anyhow, here are the 25 most common issues that can trigger an EML:
1. Exhaust and Emission System Faults
| Sr. | Problem | Description |
| 1 | Faulty Oxygen Sensor | The oxygen sensor plays a crucial role in measuring the level of unburnt oxygen in the exhaust gases. This data helps the Engine Control Unit (ECU) adjust the air-fuel mixture for optimal combustion. A faulty sensor can lead to the engine running either too rich (too much fuel) or too lean (too little fuel). It can increase emissions and reduce fuel efficiency. If the EML is triggered by this sensor, it may require recalibration of the ECU or replacement of the sensor itself to restore proper function. |
| 2 | Blocked Diesel Particulate Filter (DPF) | This issue is exclusive to diesel cars. The diesel particulate filter (DPF) is designed to trap soot and particulate matter in diesel exhaust. It helps to reduce harmful emissions. When the DPF becomes blocked, it can cause back pressure in the exhaust system. It can also lead to decreased engine performance and increased emissions. If the DPF triggers the EML, it requires professional cleaning or replacement. |
| 3 | Faulty Differential Pressure Sensor | Again, this issue only causes the EML to come up in diesel cars. This sensor measures the pressure difference across the diesel particulate filter. If it malfunctions, it may not accurately report whether the filter is clogged or functioning correctly. This can lead to improper management of exhaust flow and emissions control. Hence, the EML is illuminated as a warning of potential issues within the emissions system. |
| 4 | Choked Catalytic Converter | The catalytic converter is essential for converting harmful gases from combustion into less harmful substances before they exit through the exhaust. A clogged or damaged catalytic converter can severely impact engine performance and increase toxic emissions. If a fault is detected in this component, it will trigger the EML as an indication that immediate attention is required. |
| 5 | EGR Valve Malfunction | The Exhaust Gas Recirculation (EGR) valve reduces nitrogen oxide emissions by recirculating a portion of exhaust back into the engine’s intake. A malfunctioning EGR valve can lead to excessive emissions and poor engine performance. This issue often triggers the EML as it indicates a significant problem within the emissions control system. |
2. Intake System Issues
| Sr. | Problem | Description |
| 6 | Malfunctioning MAF Sensor | The Mass Airflow (MAF) sensor measures how much air enters the engine. It allows the ECU to calculate the appropriate amount of fuel to inject for optimal combustion. If this sensor malfunctions, it can lead to incorrect air-fuel mixtures. This results in poor engine performance and triggers the EML. |
| 7 | Faulty Throttle Position Sensor | This sensor monitors the position of the throttle valve and provides feedback to the ECU about how much air is entering the engine. A faulty throttle position sensor can result in erratic acceleration, poor performance, or stalling conditions, which may activate the EML. |
| 8 | Clogged Air Filter | An air filter clogged with dirt and debris restricts airflow into the engine, which can lead to inefficient combustion and reduced power output. This condition not only affects performance but may also trigger the EML. It necessitates the replacement or cleaning of the filter. |
| 9 | Dirty Fuel Injectors | Fuel injectors are responsible for delivering fuel into the combustion chamber at precise intervals. If they become clogged or dirty due to contaminated fuel or lack of maintenance, they may not deliver fuel effectively, leading to misfires and poor engine performance. This issue often activates the EML. |
| 10 | Vacuum Leaks | Vacuum leaks occur when there are breaks in vacuum lines that supply air to combustion cylinders. These leaks can lead to an incorrect air-fuel mixture, causing rough idling and poor acceleration. Such discrepancies often trigger the EML. |
| 11 | Turbocharger Failure | In turbocharged engines, a failing turbocharger can lead to insufficient boost pressure. This malfunction may trigger the EML. If detected, a professional assessment is necessary for repairs or replacements. |
3. Ignition System Defects
| Sr. | Problem | Description |
| 12 | Spark Plug/Glow Plug Failure | Spark plugs ignite the air-fuel mixture in petrol engines. Their failure can cause misfires, leading to rough idling and decreased power output. In diesel engines, glow plugs serve a similar purpose during cold starts. When these components fail, they disrupt normal combustion processes and trigger the EML as a warning of ignition system issues. |
| 13 | Ignition Coil Issues | Ignition coils generate the high-voltage sparks needed for ignition in petrol engines. A failure in the coil can lead to misfires or poor engine performance. The ECU detects these issues and activates the EML as an alert for potential faults. |
| 14 | Timing Belt Issues | The timing belt ensures synchronisation between engine components such as camshafts and crankshafts. A worn or damaged timing belt can lead to severe engine damage if it snaps while driving. The EML may illuminate when timing issues are detected by sensors monitoring engine operation. |
| 15 | Wiring Problems | Electrical wiring connects various components within an engine’s ignition and management systems. Damaged or loose connections can disrupt signals necessary for proper operation. It leads to performance issues that activate the EML as an indication of electrical faults needing repair. |
4. Electronic System Issues
| Sr. | Problem | Description |
| 16 | ECU Malfunction | The Engine Control Unit (ECU) manages various functions within modern vehicles by processing data from multiple sensors throughout the car. A malfunctioning ECU may produce erroneous signals or fail to respond appropriately to sensor inputs. It can also trigger the EML as an alert for diagnostic evaluation of electronic systems affecting vehicle operation. |
| 17 | Corroded Battery Terminals | Corrosion at car battery terminals can impede the electrical flow necessary for starting and running vehicle systems. This issue may affect various electronic components monitored by the ECU, leading to operational failures. Therefore, it activates the EML. |
| 18 | Software Glitches | Modern vehicles rely heavily on software for managing engine functions and diagnostics. Glitches in this software can result in inaccurate readings from sensors or improper commands sent by the ECU. This may also trigger the EML as a warning signal indicating potential faults. To resolve this issue, you might need software updates or resets by a professional mechanic. |
| 19 | Alternator Going Bad | The alternator charges your vehicle’s battery while supplying power to electrical systems when running. A failing alternator may not provide sufficient voltage for proper operation of electronic components. This condition often triggers alerts, including activation of the EML. |
| 20 | Aftermarket Modifications | Modifications such as aftermarket tuning chips or non-standard parts may interfere with factory settings or sensors designed for specific operational parameters. Such changes can lead to discrepancies in emissions control or performance metrics monitored by the ECU. If these modifications adversely affect vehicle operation, the engine management light comes on. |
5. Other Issues
| Sr. | Problem | Description |
| 21 | Loose Fuel Tank Cap | A loose fuel cap can cause vapour loss from your vehicle’s fuel system. It happens due to the evaporation of gasoline vapours into the atmosphere instead of being contained within a sealed system. This not only affects fuel efficiency but also increases harmful emissions. Thus, when detected by onboard diagnostics systems, it triggers the EML. |
| 22 | Engine Overheating | Overheating indicates serious issues such as coolant leaks, thermostat failures, or radiator problems that prevent effective cooling of your engine. When temperatures exceed safe limits, it often triggers protective measures including illumination of the EML. |
| 23 | Dirty/Low Engine Oil | Low oil levels or dirty oil can lead to inadequate lubrication of critical engine components. This not only affects performance but also risks significant internal damage if left unaddressed. The EML may illuminate when oil levels drop below safe thresholds, indicating maintenance needs such as oil changes or checks for leaks. Most engines have a separate engine oil pressure light for this purpose. Still, an engine management light might also come up due to issues with the lubrication system. |
| 24 | Failed Engine Coolant Temperature Sensor | A malfunctioning coolant temperature sensor may provide inaccurate readings about engine temperature. If temperatures rise unchecked due to this fault, it could lead directly to overheating scenarios triggering alerts, including activation of your vehicle’s EML. |
| 25 | Low Transmission (Other) Fluids | In addition to the engine oil, there are several other fluids in your vehicles. Out of all the others, transmission fluid is the most important one. Insufficient transmission fluid levels can affect shifting performance. It leads not only towards operational inefficiencies but also risks severe internal damage if left unaddressed over time. Thus, this condition may trigger your vehicle’s EML, indicating potential transmission issues. |
Can Engine Management Light Cause an MOT Failure?
Yes, an illuminated engine management light means an automatic MOT failure in the UK. So, if your EML comes up, the first thing you should be concerned about is passing your MOT test.
In 2018, stricter rules were introduced regarding the EML and MOT tests. Now, any vehicle with an active EML will fail. This applies whether the light is amber or red.
There’s a reason why EML is classified as a major fault during the MOT test. The most common reason why an EML comes on is due to the issues with emission and exhaust systems. That’s a big no for government officials. By ignoring an EML, you’re putting yourself and others at risk.
Therefore, if your EML is on, you should take your car to a mechanic for diagnosis before your MOT. Otherwise, you risk failing the test and incurring additional costs for repairs and retests.
What Should You Do When the Engine Management Light is Illuminated?
When you turn on the ignition, the engine management light comes on by default. However, once you start the car, it must go away. But if it doesn’t go away, you must take certain steps.
Your course of action upon encountering the EML should depend on its type. Let’s see what you should do when you see an engine management light of each type:
When it’s Steady Amber
Usually, there’s no need to panic if the amber engine management light comes on. It is mostly just a gentle reminder to check your vehicle and seek professional help if needed.
When the engine management light is steady amber, it indicates a minor issue. So, first, check your vehicle’s manual for specific guidance and look around for minor issues.
For instance, a loose or damaged fuel filler cap can trigger the light. Try to remember if you’re up-to-date on your vehicle’s maintenance schedule.
Next, monitor your vehicle’s performance. If you notice changes in acceleration or unusual noises, note it down. However, if everything seems fine, schedule an appointment with a mechanic soon. They may run diagnostic tests to identify the problem accurately.
When it’s Flashing Amber
A flashing amber engine management light signals a more serious issue that requires immediate attention. This often indicates an engine misfire or a problem with the emission control system.
So, the first thing you need to do in this case is to reduce your speed and avoid hard acceleration. Just become more cautious while driving and try not to drive as much as possible. Try resetting the engine management light and see if it stays off while driving.
If you experience rough idling or loss of power while driving, pull over safely. Allow your car to cool down for a few minutes before restarting. If the light continues to flash, do not drive further. Driving with a flashing light can cause severe damage to your engine and catalytic converter.
Immediately, contact a breakdown service or roadside assistance. Once you reach a garage, explain the situation to your mechanic. They will likely perform diagnostic tests to pinpoint the issue.
When it’s Steady Red
A steady red engine management light is serious and should not be ignored. This indicates a critical issue that may affect your vehicle’s safety or performance. Acting quickly when you see a red light can prevent further damage and ensure your safety on the road.
So, once you see a red engine management light, pull over immediately and turn off the engine. Check for any unusual sounds or smells coming from the engine bay. Look for leaks or smoke that could indicate a severe problem like overheating, blown head gasket, or oil pressure loss.
If you notice anything alarming at all, do not attempt to restart the engine. Call for roadside assistance or a recovery service to transport your vehicle to a garage.
Explain the situation in detail to the mechanics so they can look for any potential issues. Once at the garage, the mechanic will conduct thorough diagnostics to identify the problem.
Frequently Asked Questions
1. Is it safe to drive with the engine warning light on?
No, it’s generally not safe to drive with an engine warning light on, especially if it’s red or flashing amber. A flashing amber light indicates a problem with your vehicle’s engine or emissions system. A red EML is even worse. It indicates that your car is nearing a total breakdown.
Ignoring an engine warning light can lead to severe damage to your car. Even if the EML is static amber, it can still reduce fuel efficiency and cause performance issues.
Therefore, if the engine warning light comes on, it’s best to have your car checked by a qualified mechanic. They can use a diagnostic tool to pinpoint the issue and carry out the necessary repairs.
2. How to reset the engine management light?
There are many different ways to reset an engine management light. However, it would depend on the specific car and model you’re driving. Sometimes, a simple restart would do the trick, and at other times, you might need to reconnect battery terminals.
However, simply resetting the light does not fix the underlying issue that caused it to illuminate initially. To properly reset the engine management light, you usually need to address the issue. Once the problem is fixed, your car will automatically turn off the light after a few driving cycles.
Remember that you can’t always reset the engine management light by simple means. Modern vehicles have sophisticated onboard computers that store diagnostic trouble codes (DTCs). So, in some cases, you may need to use a diagnostic tool to clear the stored codes and reset the light.
3. Why is my engine management light on?
The engine management light can illuminate for various reasons. Common causes include issues with the fuel injection system, faulty oxygen sensors, or problems with spark plugs.
A loose fuel cap can also trigger this warning. When the onboard diagnostics system detects a fault, it activates the engine management light to alert you.
While an amber light indicates a non-urgent issue, a red or flashing light signals critical problems requiring immediate attention.
Therefore, it’s essential to investigate why the light is on as soon as possible. Ignoring it could lead to more severe issues down the line, affecting your vehicle’s performance and safety.
4. Can I reset the engine management light myself?
Yes, you can reset the engine management light yourself if you have access to an OBD-II scanner. It connects to your vehicle’s diagnostic port and lets you read and clear error codes from the ECU. But, if you’re unsure about using an OBD-II scanner or results, consider seeking professional help.
However, you should first diagnose and resolve any underlying issues that triggered the light. Simply resetting it without addressing these problems may lead to recurring alerts and potential damage to your vehicle.
5. Is there an engine management light in electric vehicles?
No, there’s no engine management light in electric vehicles as there’s no engine. However, electric vehicles (EVs) have various warning lights that may not be called “engine management” lights.
These lights come on due to battery faults, charging issues, or faults in electric motors. Just like in conventional vehicles, it’s essential not to ignore these warnings. If any warning lights appear on your EV’s dashboard, it’s important to have the vehicle checked by a qualified EV technician.
Wrapping Up: Engine Management Light Meaning
So, this is everything you need to know about an engine management light. The engine management light is a crucial indicator of your vehicle’s health. By understanding its meaning and promptly addressing issues, you can ensure your car’s longevity and your safety on the road.
Ignoring an illuminated engine management light can lead to costly repairs and potential safety hazards. So, if you see an EML come up, don’t hesitate to consult with a qualified mechanic.
Remember, regular maintenance and timely repairs are essential for keeping your car in top condition and preventing unexpected breakdowns.
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