The 5 most common causes of a check engine light!

check engine light dashboard

The other day I had an interesting run-in with my car, I was driving home when out of the blue my “Check Engine” light came on. So, first after getting my heart rate down I thought “wait my car is 4 years old it has nothing wrong with it, there has to be a simple reason for this” and there was. My gas cap wasn’t tightened all the way… “D’oh!”

So, the light is on and I pull into my driveway, I stop the car, for all you safety-nicks out there I turned it off, and did the first thing we all do in situations like this, I did a Google search. “Common causes for the check engine light to go off” and I found my problem, apparently not tightening the gas cap all the way is more common than you would think. I tightened it and viola! No more check engine light. So that got me thinking what other reasons are there for this to happen, here is the top 5, in no particular order:

there is no reason to panic or think the worst just go through the list and if it still won’t go off bring it in to Koons and we’ll help you get back on the road

We do have one caveat, if your car starts smoking or stalls completely call for help and stay with your vehicle until it arrives. Once you’re safely off the road, bring your car to the closest Koons store (there are 22 of them) and have them run a diagnostic to find the cause. You can call ahead to make sure they can handle your make and model, since some cars have special computers. But once you’re at the store, you’ll be in good hands and your vehicle will be back up and running in no time.

One: Replace Oxygen Sensor

An oxygen sensor is a part that monitors the unburned oxygen from the exhaust. It helps monitor how much fuel is burned. A faulty sensor means it’s not providing the right data to the computer and causes a decrease in gas mileage. Most cars have between two and four oxygen sensors and the code you get from the scanner will tell you which one needs replacing.

Causes: Over time, the sensor gets covered in oil ash and it reduces the sensors ability to change the oxygen and fuel mixture. A faulty sensor not only reduces gas mileage, it also increase emissions.

What you should do: Not replacing a broken oxygen sensor can eventually lead to a faulty catalytic convertor, which can be expensive to replace. An oxygen sensor is easy to replace on many cars and is usually detailed in the owner’s manual. If you know where the sensor is, you only have to unclip the old sensor and replace it with a new one.

Two: Loose or Faulty Gas Cap

You wouldn’t think a gas cap would be that important, but it is. When it’s loose or cracked, fuel vapors leak out and can throw the whole fuel system off. This causes a reduction in gas mileage and increases emissions.

What causes it: If you get an error pointing to the gas cap it means fuel vapors are leaking out of your cap. This means the cap is either cracked or just wasn’t tightened well enough.

What you should do: If your car isn’t feeling jerky or strange when the check engine light comes on the first thing you should check is the gas cap. Pull over, open the access cover and remove it, take a look at the cap to see if it has any cracks or holes in it. If not replace it and tighten it down all the way and continue driving to see if the check engine light turns off.

Three: Replace Catalytic Convertor

The catalytic convertor works to reduce exhaust gases. It converts carbon monoxide and other harmful materials into harmless compounds. If your catalytic convertor is failing, you’ll notice a decrease in gas mileage or your car won’t go any faster when you push the gas.

What causes it: Catalytic convertors shouldn’t fail if you’re keeping up on regular maintenance. The main cause of failure is related to other items on this list, including a broken oxygen sensor or deteriorated spark plugs. When it fails, it stops converting carbon monoxide into less harmful emissions.

What you should do: If your catalytic convertor fails completely, you eventually won’t be able to keep the car running. Your gas mileage will be terrible, so you should try and fix it as soon as you can. This is not an easy fix so you will need to have a professional take care and in most areas it will be part of an emissions inspection so it’s just better to have it done at a garage.

Four: Replace Mass Airflow Sensor (MAF)

The mass airflow sensor tells the car’s computer to add the proper amount of fuel based on the air coming through to the engine. A faulty one can increase emissions, cause the car to stall, and decrease gas mileage.

What causes it: Most mass airflow sensors fail because of a improperly installed (or never replaced) air filter. You should replace the air filter at least once a year to help prevent the airflow sensor from failing.

What you should do: Theoretically you can drive for a few weeks or even months with a broken MAF sensor. You will notice a decrease in gas mileage and over time the car will eventually start stalling a lot. It’s not terribly difficult to do on your own, but the process is quick enough you may want to let a mechanic handle it when you have a tune-up.

Five: Replace Spark Plugs and Wires

The spark plug seals the combustion chamber and provides a gap for a spark to jump across and initiates combustion in your engine. When the plugs are failing, the spark plugs misfire. You’ll feel a little jolt in your car’s acceleration when this happens.

What causes it: Most spark plugs and their wires in cars from before 1996 should be replaced every 25,000-30,000 miles. Newer ones can last up to 100,000 miles. Still, plugs can fail over time and so can the wires and there’s not much you can do to stop it once it starts.

What you should do: Get them replaced right away. It’s easy and cheap and your car will run better for it. Since this is part of your vehicles regular maintenance, the Koons Tech will tell you when they should be replaced when you bring it in for regular maintenance. The plugs and their wires are usually easily accessible from the hood of the car. It’s simple fix but it is a dirty one so be prepared to get your hands dirty on this one if you decide to do it yourself.

There are plenty of other possibilities that a check engine light can come on, but the five listed here are the most common. So there is no reason to panic or think the worst just go through the list and if it still won’t go off bring it in to Koons and we’ll help you get back on the road with the piece of mind that your car should be issue free. 

About Krystal Koons

Krystal Koons is the spokesperson for Jim Koons Automotive Companies, one of the country's largest privately-held dealership groups headquartered in the Washington, D.C. area. Visit us at www.koons.com.

Posted on May 16, 2014, in Automotive, Maintenance Monday, Safety and tagged , , , , , , , . Bookmark the permalink. Leave a comment.

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