The Check Engine Light Demystified

There’s one little yellow light that strikes fear in the heart of every driver. It casts a shadow of doubt over your whole vehicle. Will this be something straightforward or will the repair bill put you in debt?

The Check Engine Light has long puzzled drivers with its vague warning. When it illuminates, it's unclear if you should continue driving or get your car towed. Here’s everything you’ve wanted to know about the Check Engine Light:

What the Check Engine Light Does

The Check Engine Light has one purpose: to tell you when you have a problem. That’s all. It doesn’t tell you what the problem is; a technician will have to perform a diagnostic scan to check the affected system. It only indicates that something isn’t working properly.

The Check Engine Light is also known as a malfunction indicator light. It’s shaped like a motor and is yellow in color. Most vehicle systems run self tests under certain operating conditions, and the results are reported to their respective control modules. If a self test fails under certain parameters, your car’s Check Engine Light will come on. It could be an engine, transmission, or emissions system that didn’t pass the test.

What Does the Check Engine Light Mean?

There are two different ways the Check Engine Light can come on: solid or flashing. They mean two different things.

If the engine light comes on and flashes, that indicates an immediate concern. You need to find a safe place to pull over and turn your vehicle off. You may want to consider getting it towed to the shop. A technician needs to diagnose the concern at the absolute earliest convenience to prevent damage to your car. A flashing Check Engine Light is serious business.

If the engine light comes on solid, it may still be a reason for concern, however it doesn’t immediately need to strike fear in your heart. A solid Check Engine Light can mean something like a loose gas cap, or it can indicate a more in-depth problem like a fuel, timing, or transmission issue. Get your car diagnosed, although the urgency isn’t the same as if the light was flashing at you.

Common Reasons the Check Engine Light Comes On

The reason for an engine light can be a risk of catastrophic failure or something requiring immediate attention, or it could be nothing at all. As the car’s systems run self-tests, it is possible that a test fails and the engine light comes on, and the next test passes. The Check Engine Light may not turn off as soon as it passes, and it may not even turn off until a technician clears the code even though there is no repair required at all. Common reasons for the Check Engine Light are:

  • The gas cap was left loose when refuelling
  • Emissions-related sensors, such as oxygen sensors, have failed
  • Engine timing problems, most commonly with variable valve timing
  • Transmission failure codes
  • Engine misfire codes
  • Catalytic converter problems

There are literally dozens, if not hundreds, of other reasons for the Check Engine Light to come on. If it illuminates, have it checked out expediently. Don’t take unnecessary chances if it feels like the vehicle is not operating in a safe manner. Have your vehicle towed to the shop if you don’t feel safe driving it. If the Check Engine Light is flashing, it is in your best interest to cease driving until the light has been diagnosed and repaired.


Next Step

Schedule Check Engine Light is on Inspection

The most popular service booked by readers of this article is Check Engine Light is on Inspection. Once the problem has been diagnosed, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

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Recent Check Engine Light is on Inspection reviews

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Rating Summary
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8,017
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Dan

40 years of experience
1080 reviews
Dan
40 years of experience
Plymouth Grand Voyager V6-3.3L - Check Engine Light is on - Lawrenceville, Georgia
Mr. Dan Barber was quite patient, courteous and quite knowledgeable. From my observation, Mr. Barber appears to be quite professional.
Nissan Altima - Check Engine Light is on - Gainesville, Georgia
Dan is a super nice man that listens to your issue and does an easy to understand explanation so that you can truly take in, process and actually feel like you know what is going on with your vehicle and needed repairs. Honesty is what I felt I received. He wanted to make sure I was in a safe operating vehicle. His skill and knowledge level are exceptional. I will never use another car dealership for diagnostics or repairs. Thank You Dan!!!!!

Greg

23 years of experience
624 reviews
Greg
23 years of experience
Toyota Camry L4-2.4L - Check Engine Light is on - Phoenix, Arizona
Attention to detail and provided clear information to his findings. Acted in a Profesional manner throuout
BMW X5 - Check Engine Light is on - Chandler, Arizona
Greg was running a bit late due to business being busy but he comunicated with me very well, and let me know where he currently was and what time to expect him. Also he went above and beyond by showing me some small things that I could do myself to make my older BMW run excellent. Thanks Greg, appreciate your passion for your job

Keven

8 years of experience
187 reviews
Keven
8 years of experience
Subaru Impreza H4-2.5L - Check Engine Light is on - Spanaway, Washington
Very professional courteous respectful knowledgeable explains everything of the aspect of work and what needs to be done on the vehicle. Exceptional awesome amazing friendly and kind. 10+stars. I highly recomend friends and families if they need a experience mechanic is to ho to your mechanic and ask for Keven. Thanks again for an exceptional diagnostic repairs on my daughter vehicle. Very happy and pleased.
Hyundai Veloster - Check Engine Light is on - Tacoma, Washington
He is very informative, professional and friendly. He told us what was wrong with our vehicle in details, and gave us very helpful suggestions.

Brian

19 years of experience
138 reviews
Brian
19 years of experience
Nissan Juke L4-1.6L Turbo - Check Engine Light is on - Hampton, Georgia
Professional, knowledgeable, diagnosed problem very quickly. Provided me with feedback as to probable cause of the defect.
Chevrolet Trax - Check Engine Light is on - Covington, Georgia
Very professional/punctual & knowledgeable. I’d prefer Brian to repair my moms vehicle since I’ve established a rapport with him if at all possible when I’ve gotten my final quote that’s reasonable after choosing services/parts to perform the repair work.

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