The check engine light can be pretty scary.
It’s big, it’s yellow, and it’s fairly ominous.
Unlike some other warning lights, however, the check engine light is often pretty benign. You should still take it seriously and diagnose the problem as soon as you can, of course. But if you can’t get to the dealership immediately, don’t panic. It’s often safe to drive your car for several hours or even days with the light on.
Until recently, cars couldn’t talk to you directly. Before LCD screens and fancy modern computers, cars relied on the lights on the dashboard to communicate with their drivers.
The check engine light is a signal from your car that it’s got something it needs to tell you about the way the engine is running. It’s kind of like your phone telling you that you have a voicemail. The check engine light is your car telling you that you should plug in an OBD2 scanner.
What’s OBD2?
OBD2 (or OBD-II) stands for “on-board diagnostics 2.”
It’s a system that’s built into pretty much every car made since 1996. The OBD2 system has dozens of sensors on key components within your car’s engine. Each car uses a built-in computer chip to monitor these sensors, record data, and store messages.
When the sensors start telling the computer that there’s something fishy going on, your OBD2 system will turn on the check engine light to let you know. It’ll also store an error code that you can read back using a special scanner so you can figure out exactly what the problem is.
What Are Some Common Reasons For The Check Engine Light To Be On?
Many of your car’s diagnostic sensors are attached to some pretty mundane components. Your check engine light is often turned on because of a simple error that can be fixed in minutes with the right parts.
Here are some of the most common problems that can lead to your check engine light being activated.
The oxygen sensors in your engine are pretty important. Your engine is constantly being fed a mixture of air and fuel that it combusts to generate mechanical energy.
It’s important to keep the fuel and air levels in this mixture balanced in order to improve gas mileage and avoid engine damage.
The O2 sensor is a part that your car needs in order to figure out how much air is getting into the engine. Without a functioning O2 sensor, your car will get worse gas mileage and eventually suffer some pretty expensive side effects.
You’re normally good to drive around for a couple days, however, and it’s actually pretty easy to replace an O2 sensor yourself.
Slightly loose gas caps are a prime culprit for lighting up your check engine indicator.
There’s a sensor in your gas tank that tells your car if any gas vapor is exiting your tank. If your cap isn’t screwed in all the way, this sensor will fire, triggering your check engine light.
Even if it’s tightened all the way, the cap might be cracked or damaged. Thoroughly checking your gas cap can often solve your check engine light woes, although it can take a while before the light turns off on its own.
Use an OBD-II scanner to make sure that you found the right issue and clear the light immediately.
The catalytic converter is a part of your exhaust system that helps keep your car’s exhaust relatively clean.
Your car puts dirty, polluting exhaust fumes into one end, the converter works some magical chemistry, and significantly cleaner, less harmful exhaust comes out the other end.
Your car has some diagnostic sensors on the far side of the catalytic converter that help make sure that your exhaust is within safe levels. If your catalytic converter stops working (or stops working very well), it’ll quickly trip your check engine light.
Catalytic converters are pretty expensive and the labor cost involved in replacing one is pretty low, so it’s usually best to get this issue fixed by a mechanic.
The mass airflow sensor has a similar job to your car’s O2 sensors.
It monitors a different stage of the air intake process in order to help your car mix the right amount of air and fuel in each cylinder.
Like your car’s O2 sensor, a bad mass airflow sensor can turn on your check engine light.
Mass airflow sensors are often a bit more expensive than O2 sensors. They’re not too difficult to replace on your own, however, so you can save a bit of money on labor if you’re so inclined.
Spark plugs are used by your car to ignite the fuel and air mixture in each cylinder.
If there’s an issue with your spark plugs or the wires that connect them to the car battery, your car can suffer reduced mileage, misfires, and backfires. All of these issues cause other, more expensive damage, including damage to your catalytic converter.
If your car’s sensors detect that your spark plugs aren’t working right, it’ll quickly turn on the check engine light.
If you’ve got some experience working on cars, you could try to replace the ignition coils and spark plugs yourself, but it’s a bit tricky.
This problem is probably best left to a mechanic to solve.
How Safe Is It To Ignore Your Check Engine Light?
When your car turns on the check engine light, it’s telling you that there’s a problem. The severity of that problem can vary greatly, however, and it’s difficult to know for certain how much trouble you’re really in.
Most experts recommend that you carefully consider the context of your check engine light coming on. If your car is otherwise operating perfectly normally, it’s fine to drive for a few days or even a week before you diagnose the problem.
If your car is doing anything odd, however, you should pull over immediately and call a tow truck. Odd things include the temperature warning light being on or your engine being especially hot, the engine misfiring, the engine making a loud noise, and the engine responding oddly to accelerator inputs.
If any of these things happen, you’ll want to stop driving as soon as you can.
How Can I Fix My Check Engine Light? What Are My Repair Options?
The check engine light indicates that your car has a message for you.
You’ll need an OBD2 scanner in order to retrieve this message. It’ll give you a pretty good idea where to look when it comes to fixing your car.
Alternately, you can take the car to a mechanic and pay them to retrieve this message for you.
The steps you’ll need to take to fix your car will vary based on the exact issue that triggered the check engine light. Often, you’ll need to replace a sensor or part. Depending on which sensor or part you need to replace, this can be very cheap and easy to do yourself, or it can be incredibly expensive and require the help of a professional mechanic.
It’s necessary to retrieve your car’s error code and do some research to figure out what your repair options are.
If Your Check Engine Light Is On, Don’t Panic!
If your engine isn’t doing anything weird, your check engine light is often pretty benign. In many cases, picking up a cheap OBD-II scanner will allow you to diagnose your car’s engine problems and often allow you to fix them on your own without spending a lot of money.
Even if your car engine’s problems are too difficult for you to fix on your own, your diagnosis will help you shop for the right mechanic to get your car back on the road.
The check engine light is simply your car’s way of telling you that there’s a potential problem. Having an OBD2 scan tool will let you figure out what that problem is.
About the author
I’m Tim Miller, an automotive mechanic and blogger from Denver, Colorado. I’m the founder of obdadvisor.com, an automotive blog about OBD2 scan tools. My fanpage is facebook.com/autozikcom.
I’ve had over 10 years experience in car repair and using OBD scanners.
Some of my review articles about car diagnostic tools can be found on my own website obdadvisor.com.
