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Check Engine Light: The Most Common Failures that Trigger This Warning Light

September 10, 2019

The dreaded check engine light. Everything seems fine, you are tooling down the highway, and suddenly, that light catches your eye. You immediately take your foot off the gas, turn down the music, and listen intently to the motor. It sounds OK. What could be wrong? Am I going to be stranded? Is this going to be expensive?Sound familiar? The check engine light or service engine light is probably the second thing people fear most about their cars. (The first one being steam from under the hood). It’s easy to see why. A dead battery? You know what it is and what to do. Even steam means the car is overheating. Even if you might not know exactly why it is overheating, you know what to do. But the check engine light? What does that mean? Is the car going to explode? Stop running? Is it just a money-making scam because the car drives fine? Do I take it in right away or can I wait till payday? When the engine light shows up, most people just feel lost.There are a multitude of reasons why the service engine light turns on. However, one thing is certain: It isn’t just a money-making scam. Today’s modern cars are full of computers and sensors designed to reduce tailpipe emissions, maximize fuel economy and help you get the most out of your engine.Let’s look at what you should do when the engine light comes on your dash—and why people ignore this dashboard warning light far too often.

If My Car Runs Fine, Why Spend Money on a Check Engine Light?

If you haven’t heard that, you’ve probably thought that at one time or another. The problem may not cause your car to run differently. The truth is that the check engine light comes on because one of many parts responsible for your tailpipe emissions has failed an internal test or is operating outside of accepted parameters. Your vehicle's onboard computer flags this and turns on the service engine light to get your attention. If you let it go, this often causes damage to other parts and creates a more expensive repair scenario. So, you can spend a little now to fix the engine light problem or you can spend a lot more later when the failing part ends up damaging other parts.

The Engine Light is On. What Should I Do?

Your first instinct is correct. Turn off the radio, and listen to the engine. Does it sound any different? Is the car experiencing any problems? Do you have any red warning lights or gauges going into a red zone? Overheating? Charging system low? Oil pressure reading zero? If any of these are true, yes, you should probably stop driving as soon as possible. Some car manufacturers have a system where a service engine light that is flashing means it is an urgent issue, and you should stop driving ASAP. If the light is steady, then you can wait, and keep driving until the car can be looked at. Check your owner’s manual to see if your car has this feature.If your car seems to be running fine, it’s time to ask yourself a few questions. Did you recently get gas? The gas cap may not have been put back on or it is loose. It could even be cracked or broken. This will cause the engine light to turn on. Did you recently have any work done on the car? If you did, you should return the car as soon as possible to the location to see if the light is related to any work that was done.

People Drive for Years with the Check Engine Light On. Why Do They Ignore It?

There are many reasons to ignore things in life that you don’t like or that you feel are unreasonable. Many people ignore high blood pressure readings, speed limits and junk food warnings, although their reasons for ignoring these might be different from the warning lights on their car.The #1 reason people ignore that warning light is cash. Let’s face it, chances are that little light on your dash is going to cost you at least a little money. If you don’t have it and the car seems fine, why bother?As we mentioned earlier, the problem with this thinking is that most likely the failed part is causing damage to other parts. Or chances are, you are wasting money because the car is no longer fuel efficient. You won’t pass your next inspection due to a high level of emissions.The choice is entirely yours. You can pay now, or you can pay later. Unfortunately, there is no denying that in the end, you will pay. The longer you wait, the more it will cost you.

Top 5 Causes of a Check Engine Light

Although we know there are at least 1,000 reasons reasons that can trigger the check engine light, there are a lot of common failures. Here are the top 5 failures that cause an service engine light:

1. Oxygen Sensor (O2 Sensor)

This part measures the amount of oxygen in the exhaust gas. This helps to keep emissions down and prevents your car from burning more gas than is necessary. Cars and trucks have between one and four oxygen sensors. In most cases, only one oxygen sensor needs replacing. Not replacing this part (which averages a few hundred dollars) will cost you a burned-out catalytic converter down the road at an average price of $2,000.

2. Gas Cap Problems

The gas cap keeps fuel vapors from venting to the outside air. While this won’t hurt your car necessarily, you are hurting the environment. Of course, if something should fall into the gas tank, be it a bug, a rock, or your kid’s beanie toy, you will be paying big time to remove the gas tank and flush the system. Be sure the gas cap is on tightly. You should hear clicking sounds when it is fully closed. If you don’t hear the noise or if you see the cap is broken, cracked, has a missing gasket or is lost entirely, get a new one. For everyone’s sake. They are about $10-20.

3. Spark Plugs/Spark Plug Wires/Ignition Coils/Distributor Cap, Etc.

Some people think that tune-ups are a thing of the past. While they don’t need to be done nearly as often, they are still important. The check engine light will definitely come on if your car has spark plugs, spark plug wires, a distributor cap/rotor or ignition coils and the parts are failing and causing the engine to misfire. Replacing these worn out parts will not only improve your gas mileage right away, but they can also make the car run substantially better (assuming there's nothing else wrong). These are not expensive repairs, but the price does vary depending on how many parts you need and if you have a 4, 6, or 8-cylinder car.

4. Catalytic Converter Has Failed

This part helps to reduce the amount of harmful exhaust gas (aka "emissions") by converting the majority of it to carbon monoxide. When this goes bad, it will hit your gas mileage. Leave it go long enough, and the car will simply refuse to go more than 20 or 30 MPH. We won’t kid you: These aren’t cheap, but eventually, the car will refuse to run. So, you might as well suck it up, and pay now or add Uber to your speed dial list.

5. MAF Sensor (Mass Airflow Sensor)

This sensor tells the computer in your car how much fuel the car needs based on the amount and temperature of the air that is entering the car. When this goes bad, it can lower your gas mileage and cause the car to stall. Changing the air filter regularly will help keep this part working longer. The car will start to stall more often if you keep driving with a failing sensor.

The Bottom Line

When your check engine light is on, you are far better off calling the caring experts at Auto Lab for an appointment. Our experienced technicians excel at diagnosing check engine light issues correctly the first time. For us, this is not a guessing game. We get to the heart of the matter immediately, and we will always provide an estimate and explain the situation before we make any repairs. Don’t risk a bigger repair down the road. Auto Lab is just a phone call away, so call now.

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