Check Engine Light: What is It Telling You? Deciphering Its 5 Common Causes

The check engine light is a critical part of a vehicle’s onboard diagnostics system. Yet it’s also one of the most ignored issues by car owners. Sounds familiar? You should know that when your car’s check engine light comes on, taking it for granted can lead to problems that often occur sooner rather than later—problems ranging from increased fuel consumption to complete engine replacement. The longer you wait to identify the cause of your check engine light, the more you leave your car at risk of more complex—and expensive problems.

What is the check engine light saying?

In fairness to motorists, a check engine light can signify lots of different problems, and if you don’t know what you’re up against, the easiest recourse is to simply give up. Now with that in mind, if the light comes on, it will either blink or remain steady, depending on the type of problem you’re facing. A steady light means that the problem doesn’t require immediate attention. If it blinks however, you could be in for a lot of trouble.

“But there’s nothing wrong with the car!”

We have some good news and bad news. The good news is the technology in today’s cars are so advanced that computers will attempt to compensate when there’s a problem. Thus, you may not observe any drop in performance even though your engine may already be guzzling fuel or expelling copious amounts of polluting CO2 into the atmosphere. The bad news is, automotive computers will keep the compensating thing going until it can no longer do so. When that happens, it’s usually because extensive damage has already occurred.

Don’t panic

When the check engine lights turns on, take heart, because all is not lost. In fact a couple of reasons that trigger the check engine light are simple to fix yourself. From easy to the complex, take a look at five of the most common issues.

1. Loose gas cap

For such a tiny thing, the gas cap can certainly cause big problems. When it’s loose or damaged, fuel will evaporate, and this can wreak havoc on the fuel system as a whole. Try tightening your gas cap and see if it solves the problem. Keep in mind that it may take several tries before the engine light shuts off. If that doesn’t work, then your problem lies elsewhere.

2. Busted spark plugs

Spark plugs do heavy work. It’s their job to initiate the combustion in your engine, and to do so, they need to fire up to 50 sparks a second, depending on the model. All that work eventually takes its toll, and when the plugs start to fail, misfiring occurs. You’ll feel your car jolting as you step on the gas when this happens. There’s not much you can do with problematic plugs, except replace them right away. Spark plugs are fairly easy to replace—simply check your vehicle owner’s manual for instructions.

3. Faulty oxygen sensor

As the name suggests, the job of an oxygen sensor is to detect the amount of unburned oxygen from the exhaust. If it is faulty or damaged, it cannot supply the right information to the automotive computer, which can result in decreased gas mileage. Like spark plugs, oxygen sensors are easily replaced, and a review of the owner’s manual should provide you with the information you need.

4. Damaged mass airflow sensor

The mass airflow sensor tells the computer how much fuel to add to the mixture based on the amount of air entering the engine. A defective sensor can introduce too much fuel into the mix, potentially decreasing gas mileage and even cause engine stalling. Mass airflow sensor damage is often the result of not replacing air filters as scheduled. Prevent your mass airflow sensor from failing by sticking to your air filter’s replacement schedule. If the sensor needs replacing, the task is not difficult to do on your own.

5. Overheating catalytic converter

The catalytic converter is a part of a vehicle’s exhaust system, and its job is to turn toxic carbon monoxide into less harmful carbon dioxide, which can be breathed by plants. The biggest sign of a catalytic converter problem causing your check engine light is when the car won’t go faster when you step on the gas. It's likely that your converter got clogged, and soon, with exhaust fumes having nowhere to go, pressure and temperature will mount, superheat the catalysts inside and destroy them completely, effectively rendering the assembly useless. Unless you’re an experienced mechanic, better leave the replacement of a catalytic converter in the hands of an expert.

These are just a few of the reasons why a check engine light can come on. If in doubt, have the vehicle checked by a qualified service technician as soon as you can.