Car Repairs: Why Has Your Engine Warning Light Come On?
Your car’s dashboard is full of warning lights, but few are as concerning as the engine warning light. When this illuminates, it’s your vehicle’s way of telling you something isn’t right. But what exactly does it mean?
Sometimes the issue is minor, but in other cases, it could indicate a serious problem that needs immediate attention. Here are some of the most common reasons why this warning appears, what to do and how you could prevent it.
One of the best ways to prevent unexpected engine warning lights is through regular servicing. Routine maintenance helps identify potential issues before they become costly problems. While not all faults can be avoided, scheduled servicing significantly reduces the risk of costly repairs and keeps your car running efficiently.
What does the engine light mean?
Your engine warning light can either flash or remain solid. Typically, the color of the light will indicate the severity of the issue:
- Amber Light: A non-urgent problem that should be checked soon.
- Flashing Light: A more serious issue that requires immediate attention.
- Red Light: A critical fault -pull over safely and seek roadside assistance.
Despite some issues being more urgent than others. It is always best to get problems checked out as soon as possible. But don’t worry, this doesn’t have to be costly, having a warranty in place ensures you’re protected from unforeseen repair costs, giving you peace of mind and helping you avoid those expensive repair bills.
Common reasons for an illuminated Engine Light
Fault 1: Emissions System Fault
One common reason your engine light may come on is a fault with the oxygen sensor. Car manufacturers must carefully balance performance, efficiency, and emissions to reduce environmental impact. The oxygen sensor plays a crucial role in this by monitoring the fuel-to-air ratio to ensure your engine burns fuel efficiently.
If the sensor detects an imbalance, your engine may run too "rich" (excess fuel consumption) or too "lean" (insufficient fuel), affecting performance and emissions. In some cases, the issue may stem from a faulty sensor rather than an actual fuel imbalance.
To resolve this, a mechanic may need to recalibrate or reprogram the engine control unit (ECU) or replace the oxygen sensor altogether.
Fault 2: Blocked Diesel Particulate Filter (DPF)
If you drive a diesel vehicle, the diesel particulate filter (DPF) helps trap harmful particles from the exhaust. Over time, these filters can clog, especially if the car isn’t regularly driven on long journeys at higher speeds. This can trigger the engine light or a separate DPF warning light. A forced regeneration by a garage can help clear the filter.
Fault 3: Ignition System Fault
If you didn't know your car’s ignition is a bit more than just the turning of the key, the ignition is responsible for burning fuel, making the engine work.
Spark plugs in a petrol engine are part of the ignition system, and they provide the spark that burns the fuel in the combustion chambers. However, in a diesel car, no spark is needed to burn fuel, the action of the piston compressing on the fuel and air is enough to make the mixture combust.
Starting a diesel engine on a cold day, however, leads to the glow plug heating the combustion chamber to make the whole process easier.
Both the spark and glow plug’s power come from the ignition system. In a petrol car a high voltage is needed to create the spark that ignites the fuel, and this is provided by the engine's coils. Most modern cars have a coil for each cylinder, and if it develops a fault the fuel in the cylinder won't burn effectively. This may not only cause the engine to run down on power but can also cause damage to the catalytic converter.
A problem with the glow plugs in a diesel car is usually indicated by a separate warning light but in petrol engines spark plug and coil issues are indicated by the engine light. Repairs generally involve the replacement of one or more spark plugs, spark plug leads or coils.
Fault 4: Mass Airflow Sensor
The mass airflow sensor or MAF is a key part of an engine running effectively. The computer in your car uses the MAF to calculate how much fuel is needed in the combustion chambers to match the amount of air flowing into the engine.
Your car will only be able to guess this information without the MAF and your computer will have a 'safe' set of parameters to keep your car running if a fault arises, but this can sometimes be triggered by inaccurate or missing data.
The MAF is mounted near the top of the engine where it's in the path of the air that has just passed through the air filter. An incorrectly installed or missing air filter can damage the sensor by letting harmful particles into contact with it.
It could however be a clogged air filter triggering the warning light as a lack of air will be forcing the engine to run 'rich'. This is fixed by cleaning the air filter and best done by your garage.
Fault 5:Loose Fuel Cap
One of the simplest reasons for an engine light to turn on is a loose or damaged fuel cap. Because your car’s fuel system is pressurized, a poor seal can disrupt fuel flow and trigger the warning. Checking and properly tightening the cap might be all it takes to resolve the issue.
What should you do if your engine fuel light comes on?
If your engine light appears, follow these steps:
- Check if the light is flashing or solid. If it’s flashing or red, pull over safely and call for assistance.
- Inspect your fuel cap. Tightening or replacing it might solve the problem.
- Pay attention to performance changes. If your car feels sluggish, misfires, or makes unusual noises, seek immediate help. Regular car servicing will help you identify and fix issues before they become costly repairs.
- Get a diagnostic check. A professional mechanic can help pinpoint the exact cause of the problem and walk you through your options.
Further Reading
When Can You Buy Car Warranty Protection
Motornomics: How To Drive Your Car Forever
Tyre Markings: Understand The Writing & Codes On Your Sidewall
