What is the Check Engine Light
What is the Check Engine Light:
The check engine light is one of the most vital warnings in the vehicle. Anytime the light sets, it is the vehicle’s way of letting you know something is not right, and the vehicle is not running as efficiently as it should be.
Why does it come on?
The check engine light will set due to anything from a bad spark plug to a broken wire. As a result, we get codes with different meanings/origins.
When the light comes on it is never a fun sight to see, but it is there to help us prevent more serious damage. So, in the long run, it will save you a nice amount of money if you keep attentive to the needs of your vehicle.
The check engine light will flash when there is a severe issue present that can cause engine/catalytic failure. so please, if you see the light flashing get it checked out and do not keep driving it.
Below will be listed a lot of the major causes/concerns that are presented when the check engine light illuminates
Causes:
Fuel System:
Fuel is vital to engine operation, therefore, if there is an issue in the fuel system then it will illuminate the light to warn you.
Usual causes are bad fuel pumps/filters, bad/dirty fuel is often a culprit as well. Anytime the Engine detects low or high fuel pressure it will set the light.
Exhaust System:
The exhaust system is there to help the engine breathe out all burned vapors from the engine power stroke. If the exhaust system develops a leak or becomes plugged the check engine light will illuminate to warn you that the engine cannot properly breathe. The o2(oxygen sensors) in the exhaust are one of the main inputs for engine data.
The o2 sensors measure and watch for the correct levels of fuel/air in the exhaust.
Emission system:
The evaporative emissions system is present to help minimize atmospheric vapor leaks. It cycles fuel and fuel vapor back to the fuel tank as well as the evaporative canister(used for storing excess gases). If there is a leak in the system it will set the check engine light.
Transmission:
The transmission only has a separate warning on some model vehicles, so when there is a transmission warning it will usually illuminate the engine light and set a transmission code. Sometimes it will also cause the engine to go into reduced power mode. Throttle issues are big contributors to transmission problems, so be thorough.
Security/Theft system:
The theft system uses radiofrequency broadcasts that monitor the vehicle and ignition system. If it sees an attempted theft or develops an issue with the key/remote it will inhibit the engine from starting and will set a warning.
Sensors:
There are many sensors on the vehicle that can cause a warning to illuminate. Getting the codes scanned will reveal whatever sensor/system the problem is originating from.
Cooling system:
If the engine detects a cooling system issue it will set a check engine light. It can also send the engine into a ‘limp’ mode to prevent overheating and damaging the engine.
Timing system:
If the engine develops a timing issue the check engine light will illuminate to help prevent possible engine damage. It can be anything from a tensioner to a bad belt.
Checking the Codes:
If the check engine light is on, the first thing to do is get the car scanned and see what code(s) is present.
I highly suggest grabbing your own inexpensive scan tool to keep at home. I can give a few good recommendations if needed.
Most auto parts stores will scan the codes and give a free code printout.
Be sure to check out our write-up featuring other vehicle warning lights here!!
Please be sure to leave questions and comments below!
Affordable Code Reader available here!
Different CEL Symbols
Thanks for sharing these common issues that might be the root cause of a lit-up check engine light. I’ve been meaning to get one of the scanners for our household, but not sure which models would be best. Do you know if the scanners work on both regular fuel-powered cars and also hybrid vehicles? Ideally I could find one that does both so that it would work for all of our vehicles.
You are very welcome, thanks for stopping by.
I always recommend people get a scanner that can read engine codes, as well as airbag and ABS. Nowadays you can find them fairly affordable for a basic setup. I have one linked above that will read engine/Airbag/ABS, it is listed right about $100 on Amazon, which is not bad considering my personal scanner was over $2500, and that is on the cheaper side of professional scan tools haha
I found your article after having an interesting experience with my “check engine” light. When my light came on, I took the car for service. The oil and filter were changed, fluids checked and transmission checked. When I left the garage the light went on again. I went home for the night an read my bill. It said, “Replace gas cap.” I did and the light went off. Apparently modern gas caps maintain a certain amount of pressure. If it lowers, the light goes on. Who knew? Probably you did. Thanks so much for the article.
Yep, that is actually a pretty common failure. The fuel tank and fuel system are a closed system that is monitored by a pressure sensor in the tank, the light was setting due to a detected low pressure in the fuel tank. The gas caps have an O-ring on them, and when it wears out it will cause gas vapors to escape the system.
Thanks, that’s very informative post. I’m not a car geek but it often happened to me, this icon light on in my car. At first I ignored it, and after some time my car stopped on the green light, on a busy street, in the middle of the city center. Super stressful situation as the car didn’t want to start again. Pushed it to the sidewalk, which was also super busy with people and called for my brother for help. Fortunately, before he come to tow, it finally started again after almost an hour of trying, so at least I could go back home. Funny thing after leaving my car at the mechanic, car came back fully working but the light was still on, he said it’s gonna be like that, sometimes is off though but the problem haven’t appeared since then, knock on wood. So, anyone reading that, don’t ignore it!
Ahhh man that is a super stressful situation indeed! Even as a professional, I still get stressed when a car stalls on me in the middle of traffic, really easy for the panic to set in, that’s for sure.
That is interesting, I wonder if it has a module or sensor that acted up. If you ever see what the code is let me know and I can look into it a little bit for you 🙂
I never knew there were so many reasons that a check engine light could be triggered. My fiancé likes to work on cars and do as much of the work on our cars as he can. So, the Code Reader might make a good present for him in the future. I’d never even thought of something like that.
I think this is a great article for anyone who wants to learn more about cars in general, or maybe just the problem their car is currently suffering from. You give great information that maybe not everyone knows.
Yeah a lot of people have no idea how much goes into the operation of a vehicle, but that’s why I am here 🙂
Here’s a cool fact, Most modern vehicles have over a mile of electrical wire running through them, so wiring issues on some cars can be a bit of a problem haha.
That is awesome, it is good to have somebody close by that can help you with your vehicles, having to go to a shop all the time can be pretty annoying.
Hello there,thanks for sharing this awesome article……Some people like me freak out when they see the check engine light. “They just put a piece of black tape over the dashboard light and keep driving but i have a question to ask What should you do if the check engine light comes on and it’s steady rather than flashing?
You are very welcome 🙂
Usually, you will want to act a bit quicker if you see the light flashing. If it is on steady, but not flashing, that means the system has detected an issue but it is not critical. If the light starts flashing that means it could lead to a critical failure.
hello there, thanks for sharing this awesome article it would be of great help to the public as it has been of help to me,some times this light is usually accompanied by a sinking feeling in the pit of your stomach. Also this light could be a minor issue, such as a faulty gas cap, or it could mean something more serious, such as a misfiring engine. In many cases, it means that you’ll be visiting the car dealer to repair the issue and get the light turned off.
You are very welcome.
Yeah, it can be something as simple as a dirty air filter that sets the check engine light or it could be a worn-out mechanical component. That is why it is nice that modern vehicles have trouble codes in order to point you into the right direction of diagnosis.
I really find this information very interesting, despite the check engine light being something so common we often do not know the reason and although it may be something simple as you mentioned in your article, it can also be something serious, but thanks to this we can at least give ourselves an idea of all the possible scenarios, and what we can do about it.
Once again I thank you for taking the time to collect this information.