The orange engine-shaped icon that lights up on your car’s dashboard is set to illuminate when the car’s electronic brain detects that something is amiss. It’s the engine or “check engine” light, as it’s known worldwide.
If you see this light come on, there’s no need to panic. It doesn’t necessarily mean you have to invest a huge sum of money to fix the problem. The issues that trigger this light to come on are sometimes simple and easy to address.
However, this doesn’t mean you should ignore it when the “check engine” light is illuminated; you should investigate the problem. Remember that when this light comes on, it stores an error code that can be read with an OBD2 scanner to diagnose the issue.
Here are the top 10 most common defects that can trigger the “check engine” light:
Faulty Oxygen Sensor
The oxygen sensor (also called an O2 sensor or lambda sensor) measures the amount of unburned oxygen in a car’s exhaust system. This sensor sends data to the Engine Control Unit (ECU), which uses it to regulate the air-fuel mixture entering the cylinders. An engine can run with a faulty O2 sensor, but the car will consume more fuel than usual. Over time, a faulty O2 sensor can also damage other components, such as spark plugs or the catalytic converter. It can also cause a vehicle to fail emissions testing during inspection.
Loose or Missing Fuel Cap
A loose fuel cap is one of the most common reasons the engine light illuminates. The fuel cap is a crucial part of the fuel delivery system. It prevents fuel vapors, in particular, from escaping the tank and helps maintain the correct pressure throughout the system. If the check engine light comes on immediately after refueling, pull over and make sure the cap isn’t loose or forgotten on top of your car (a common mistake among drivers). Sometimes, the cap needs replacement, but it’s not an expensive part.
Catalytic Converter Failure
The catalytic converter, or simply catalytic, is integrated into a vehicle’s exhaust system. It transforms carbon monoxide generated during the combustion process into carbon dioxide. Every modern vehicle is equipped with a catalytic converter. Regular maintenance, such as oil changes, is essential to keep the catalytic converter functioning properly. If you live in the city and drive short distances, occasionally take your car on the highway to prevent the catalytic converter from clogging, and be mindful of unusual noises or exhaust smoke.
Faulty Spark Plugs or Ignition Coils
An ignition coil generates the electricity spark plugs need to ignite the air-fuel mixture in each cylinder. Older cars have a single ignition coil, while modern cars use one coil per cylinder. If your car has a V8 engine under the hood, you could have 8 separate coils, for example. For reference, the Bugatti Chiron has 16 ignition coils. Regardless of how many you have, a faulty coil will trigger the check engine light. Keep in mind that a diesel engine doesn’t have ignition coils or spark plugs. Speaking of spark plugs, they can cause various problems when worn or dirty, including engine misfires. Changing spark plugs is a relatively straightforward task that you can do in your driveway.
Faulty Spark Plug Wires
Spark plug wires transfer electricity from the ignition coil to the spark plug. Without them, the air-fuel mixture in the cylinders can’t be ignited. The vast majority of vehicles use a single wire per cylinder, but some models (especially older Mercedes-Benz vehicles) have 2 plugs per cylinder, hence two wires. Symptoms of faulty plug wires include rough idling, poor engine performance, and increased fuel consumption.
Malfunctioning Mass Air Flow (MAF) Sensor
The mass air flow sensor plays a crucial role in gasoline and diesel engine operation. It has a direct impact on the amount of fuel injected (gasoline) and the recirculated exhaust gas flow (diesel). Common symptoms of a faulty mass air flow sensor include high or unstable idle speed, increased fuel consumption, and reduced power.
The mass air flow sensor is responsible for transmitting the volume of air entering the engine, which the Engine Control Unit (ECU) uses to calculate the engine load.
Aftermarket Alarm System
An aftermarket alarm system can wreak havoc on your car if not installed correctly. It can drain the battery, trigger the check engine light, or simply make it impossible to start the engine. If the issues above sound familiar, you’ll need to have the alarm system repaired, reinstalled, or replaced entirely by a competent mechanic. Proper installation may cost a bit more, but the peace of mind that comes with a fully functional alarm is priceless.
Vacuum Leaks
Vacuum is a fundamental principle in the operation of certain car parts and systems, such as power brakes, the turbocharger, or various valves. Several parts make it possible to create a vacuum, including the vacuum hose and vacuum pump. In the case of power brakes, the system works based on pressure differences between two chambers—one at atmospheric pressure and another in a vacuum state. The vacuum pump’s role is to remove air to create a vacuum. When it ceases to function, the vehicle loses its power brakes.
Faulty Exhaust Gas Recirculation (EGR) Valve
The Exhaust Gas Recirculation (EGR) system reduces the amount of nitrogen oxide emitted from a car’s engine and helps it run more efficiently. It redirects hot exhaust gases back into the combustion chambers, heating the fuel and facilitating combustion. It also reduces emissions.
The EGR valve can get clogged or fail entirely. If you’re mechanically inclined, you can remove the valve, clean it, and reinstall it relatively quickly. If the valve needs replacement, be prepared to pay at least €400 for a new, quality OEM unit.
Dead Battery
The battery is as simple as it is important. Without it, your car won’t start, illuminate the road ahead, or charge your phone. Today’s batteries last much longer than older ones and require no maintenance. The price of a new battery depends on the make and model of your car, but you can expect to spend at least €100 for a quality battery.
Changing or charging a battery on your own is a relatively easy task, but keep in mind that, on some modern cars, the battery is under numerous plastic covers and could be somewhat challenging to access.
