Understanding Your Car’s Check Engine Light

Uh oh! Your check engine light has turned on — the last thing any car owner wants to see. While this can be a frustrating issue and raise fears of costly repairs, this may not be the case. It’s important to understand what your check engine light means and what could be causing it. Today, we’ll explain to you everything you need to know about your check engine light. 

What Does a Check Engine Light Mean?

Your car has an internal computer that monitors your vehicle’s system to ensure they are operating correctly, including your engine. Whenever this computer detects a problem, it’ll give you the corresponding warning on your dashboard, including the check engine light.

There are two different ways your check engine light will turn on which means two different things. If your check engine light turns on and is just a solid yellow light, then you should be aware something is wrong and try to diagnose the problem, but your car is not at any immediate risk. 

On the other hand, if your check engine light is a solid red or orange or if it’s flashing, then you should stop driving as soon as you can safely pull over. This indicates that your car is in immediate danger of damage and driving any further can be dangerous for both you and your vehicle.

Reasons for Check Engine Light

A check engine light is tricky because there can several different things that may be wrong. Here are some of the most common reasons we’ve seen for check engine lights. 

Loose Gas Cap

One of the simplest reasons your check engine light will turn on is your gas cap is not sealed. This is a pretty easy fix to do yourself if it was just that you didn’t tighten the gas cap all the way. Your car’s internal computer is expecting a vacuum seal on the gas, so when the cap is loose, it’ll turn on the check engine light. 

If you tighten the cap and you’re still getting a warning, the gas cap may be cracked or have a poor seal. In this case, you’d need to replace your gas cap in order to keep your gas tank sealed properly and have the light turn off.


Spark Plug Failing

Your engine needs to have an operating ignition system and combustion chamber (see photo) in order to function. When any of these ignition or combustion parts start to have problems, it will almost always lead to a check engine light. 

One common issue we see in this system is a failure in the spark plugs. As the name suggests, spark plugs give the necessary spark to start ignition and combustion. All spark plugs will eventually wear out as they’re used, and while this varies in time, the standard is to replace them every 100,000 miles. 

A good way to tell if the issue is the spark plugs aside from the check engine light is if you’re also having trouble starting the car or the engine sounds rough, either while idle or with a knocking noise while driving.

Oxygen Sensor

Oxygen sensors ensure your car has the proper amount of oxygen and fuel in order to conduct combustion. Too much oxygen can cause your car to start using more gas and decrease your fuel efficiency. Too little oxygen can cause your car to decrease the amount of gas, leading to a sluggish car performance or a misfiring engine. 

This is a very common reason for your check engine light to turn on. Oxygen sensors will need to be replaced eventually, and these issues can occur the closer you are to this period. You’ll want to consider replacing your oxygen sensors once you reach about 50,000-60,000 miles on your car; if your check engine light turns on around this mileage,  it is very likely that it’s the oxygen sensor that, fortunately, is an easy, cheap car repair. 

Catalytic Converter

Catalytic converters convert any toxic or harmful gases your car produces into environmentally-friendly, harmless gases. Over time, your catalytic converter can become clogged or damaged. If this happens, your check engine light will turn on. A sure sign it’s your catalytic converter is if you can smell sulfur or rotten eggs. 

This problem will need to be fixed quickly. As the catalytic converter clogs more and more, it can cause it to heat up to temperatures as high as 2000 degrees Fahrenheit. This can permanently damage your engine and cause even bigger repairs. 

Unfortunately, a check engine light caused by the catalytic converter can be a costly issue to fix, but it’s not one you’ll want to ignore. 

What Do I Do If My Check Engine Light Is On?

There are several steps you can take when your check engine light turns on. 

  • First, see what type of light it is. If it’s flashing or is a solid red or orange, pull over when you can safely. If it’s solid yellow, you can continue driving but shouldn’t wait too long to check for the problem.
  • Check your gas cap first whenever you’re not driving. If it’s just that you didn’t tighten it completely, this will be the easiest and quickest fix.
  • If the gas cap doesn’t turn off the check engine light, go to your local mechanic to get the issue diagnosed. We here at City Auto Repair can diagnose your car for you, find what the source issue is, and direct you on what to expect from the repair. 

Check engine lights are never fun, but it’s not a reason to panic. It means your car is warning you properly so that you can address the issue and get back on the road again once it’s repaired. 

City Auto Repair Can Help You Figure Out Your Check Engine Light

We’re here to help you whenever any light or warning comes on your car. We’ve been serving Gainesville with auto repairs for over 40 years and are the experts in car diagnostics. If you’re having concerns about your vehicle, don’t wait to make the call, contact the City Auto Repair team today!