What Does the Check Engine Warning Light Mean?

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Since the early 80’s, the check engine light can be found on pretty much every car made. The check engine light was implemented to try and keep engines running efficiently while reducing fuel consumption. As you drive along, the car’s computer monitors different aspects of the engine and exhaust to determine whether everything is working as intended. Anything abnormal and the computer will illuminate the light to alert the driver that a fault has been detected. Check out some of the car diagnostic tools via ProCarReviews OBD2 recommendations, to help you read the exact fault that has been detected.

While many dislike the check engine light and tend to ignore it, the check engine light can be a very helpful warning as long as you understand what it means.

What the check engine light means

As mentioned earlier, the main reason why the light was introduced in the first place was to try and keep engines as efficient as possible. When you first start the engine, the light should illuminate for a few seconds to verify that the bulb is working. You should replace the bulb if you don’t see it come on during startup. If the light stays on after startup, it indicates that the computer has noticed a fault somewhere and stored a code in memory to help identify the problem.

Some common reasons for the light to come on include faulty spark plugs, malfunctioning engine sensors, or even a loose gas cap. Check the gas cap first and ensure that it is fully tightened. If the gas cap doesn’t appear to be the issue, you’ll need to hook up a scan tool to the car and read the code to understand more of what’s going on. Usually the issue is fairly minor, but this warning light should never be ignored as small issues tend to develop into bigger, more costly ones, if neglected.

If you ever see this light flashing, that is an indication of a serious misfire occurring in the engine. You should pull over as quickly and safely as possible and shut the engine off. The misfire can allow unburned fuel to enter the exhaust system and then reach the catalytic converter. The catalytic converter operates normally at several hundred degrees so the fuel ends up burning inside the exhaust which raises the temperature even more. Too much heat and the catalytic converter will be toast in no time and you’ll have an expensive repair bill on your hands. You should have the vehicle towed in this situation to prevent any serious damage from occurring.

Is it safe to drive with the check engine light on?

Even if this light is on, it doesn’t mean that the fault is currently happening. Certain faults may only happen every now and then, but the light will remain illuminated until certain parameters have been met. Usually, this involves driving the car normally and if no fault has been detected for a while, the computer will turn off the light automatically. It’s always best to have the light checked out, but sometimes driving normally for a few days can shut the light off and you won’t see it again.

If you are able to notice a difference in how the car drives, then it is likely the light won’t turn off until the issue has been resolved and you should not ignore this warning in this situation. As mentioned, if the light is flashing, significant damage is a real possibility and you should not drive the car until the issue is resolved.

If your check engine light is on and you’d like to know why, our certified technicians are always available to help you determine the cause of the problem.


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Jay

36 years of experience
745 reviews
Jay
36 years of experience
Ford Ranger - Check Engine Light is on - Chino, California
Great experience. He showed up early and fixed the issue that I requested (AC recharge) as well as recommendations on other issues he saw on the vehicle.
Volkswagen Beetle - Check Engine Light is on - Bloomington, California
He was very thorough with explaining the possible issues with my vehicle. I would definitely recommend to friends if looking for a mobile mechanic.

Kevin

23 years of experience
309 reviews
Kevin
23 years of experience
Nissan Sentra - Check Engine Light is on - Atlanta, Georgia
Kevin is very knowledgeable about all makes and models with numerous years of experience. He is very professional and makes sure the customer does not have to worry about car troubles.
Ford F-150 - Check Engine Light is on - Atlanta, Georgia
Great Communication ! Very thorough, businesslike. Not in a hurry..Friendy. Really explained everything in detail. Would 100% use again!

William

16 years of experience
64 reviews
William
16 years of experience
Jeep Grand Cherokee - Check Engine Light is on - Denver, Colorado
Couldn’t be happier with my experience with William. Will happily recommend him to everyone and will definitely be using him again. Fantastic service.

Andrian

31 years of experience
112 reviews
Andrian
31 years of experience
BMW 525i - Check Engine Light is on - Fort Lauderdale, Florida
Highly recommend Adrian for all automotive services. Very professional and extremely knowledgeable about everything related to our car. He explained everything so we knew exactly what was needed and went above and beyond to make the process easy. I would never use another person to work on our cars. EXCELLENT OVERALL!!

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