Your Check Engine Light Came On – Now What?

An in depth guide on what to do when your check engine light turns on Your Check Engine Light Came On – Now What?

Everyone hates it when the dreaded “check engine light” comes on in their car. It’s a momentary heart attack followed by more than minor annoyance. It’s inevitable that, at some point in the lifetime of any car, it will have some issue or another that will trigger the check engine response. That check engine light is far from a bad thing, though; it’s a tool, an indicator is designed to protect you and make sure your car gets taken care of as quickly as possible. But what exactly does a check engine light mean you have to do? It’s a pretty vague phrase, which can be interpreted as anything between “pop open the lid and see if anything’s obviously wrong” and “oh god, this car needs to get to an auto shop immediately.” In reality, both of these extremes are not the right way to go. Here’s an in depth look at what you should do when your check engine light does come on.

Greyscale Photography of Car Engine

What Does the Check Engine Light Mean?

On the face of it, it’s quite simple. The check engine light comes on and, generally, it means you need to check your engine or have it checked. But what exactly is the mechanism that does this, and what does it really mean? Fundamentally, it means the computer is recognizing that there’s some issue with the car in general. Computers haven’t always been an element of cars, but since the 80s, computers have had a larger and larger role in the functioning of vehicles. If you have a modern vehicle, you can obviously tell that a computer is controlling things like the music and the A/C; after all, most modern cars have an actual computer screen built right into the console. But the computer actually governs a great deal of how a car works, managing everything from emissions to engine controls like ignition or speed to controlling the transmission (in automatic cars). If any aspect of the computer’s connection or control of the car is interrupted, then that will trigger a check engine light response.

Don’t Panic

The vast majority of the time, having a check engine light go off is not a serious issue. You don’t need to pull over to the side of the road, call triple AAA, or peel off towards an auto body. Unlike some of the other indicators that you might get from your car, a check engine light is just letting you know that there’s a potential problem brewing. Occasionally, there’s going to be some sort of serious cause behind the check engine light, but far more often than not, the issue is going to be a relatively small one that isn’t catastrophic. Regardless, driving around with an issue, no matter how initially small, can snowball into something very significant, so don’t take the call not to panic to mean that you don’t need to do anything. It just means that, if needs be, you can wait a few days or a few weeks before getting to the problem. But don’t go taking it into the auto body just yet. There are a few things that you’re going to want to check for, because it’s possible that the whole thing is a false positive, and you don’t have an issue at all.

Look For Obvious Issues

If you do see the check engine light, a good first step is to see if there’s anything that is clearly the cause of it. That means pulling over (when it’s safe to), and taking a look at the functional parts of the car, mainly underneath the hood. If there’s something rattling, shaking, vibrating, or pouring out smoke, then that’s a good indicator that you do have a serious problem on your hands. If there’s nothing immediately apparent, however, you’ll be able to take care of the issue in a more leisurely fashion.

Free stock photo of man, person, hands, blue

Check Your Gas Cap

Just about the most common cause that you’ll ever encounter for having a false check engine light is just that the gas cap is loose, or possibly cracked. Therefore, the first thing you should ever do when you see that check engine light is to check and see if the gas cap is loose or cracked. If it’s loose, simply tighten it up and hop in the car. Don’t feel disheartened, however, if the check engine light doesn’t go away immediately; it will sometimes take a few trips before the car registers that the issue is taken care of. If the cap is cracked or missing, which has happened to drivers before, then all you need to do is acquire a new gas cap, which are not generally very expensive.

Reduce the Strain on the Vehicle

Try to determine if there was anything that you were doing with the vehicle immediately before the check engine light came on that might have caused an issue. If, for instance, you’re pulling a heavy load behind a car that doesn’t often tow anything, or if you were trying to beat a personal best on the Autobahn, then you’ve probably already identified the cause of the issue. As soon as you can, stop doing whatever it is you were doing that you think caused the issue. If it is an instance of pushing the car too far, then it’s probably going to be a good idea to have the car looked at by a professional, because you don’t know what type of damage you might have done.

Use Built-in Diagnostics (If Available)

For most readers, this step won’t be an option, but there are some modern cars, especially modern luxury cars, that actually come with a built in method of diagnosing issues. The interface will connect directly with the car’s computer and identify the issue, from which point you can bring it in to a mechanic if you need to, or take care of the issue on your own if you’re capable.

Audi Vehicle Interior

If you’ve not identified any obvious cause of the check engine light, it isn’t from a loose gas cap, it’s not because you were pushing your vehicle harder than it can take, and you don’t have any built-in diagnostic equipment, then you have three options of what to do next:

Option #1: Take it to the Shop

By far, this is the most common option when it comes to dealing with a check engine light. It’s the most hands-off and easy option; you simply drive to your mechanic, hand them the keys, tell them about the light, and sit for a while waiting to find out the news. The advantages of this option is that it’s easy and doesn’t require any input on your end. On the other hand, mechanics are notoriously expensive, and it’s possible that you’re paying for a service you don’t need. Always find out what the cost to diagnose an issue is upfront, and be willing to shop around a little bit to determine what auto shop will be best for you. Once they diagnose an issue, they will quote you on the further price that you need to pay in order to fix the problem. If you’re lucky, there is no problem, and the check engine light just had an internal issue, but even in such a case, you’re still out the diagnostic fee. So what options are there to those who don’t want to spend money at an auto shop?

Option #2: Purchase a Diagnostic Tool

The same tool that an auto shop will use to determine what the issue is with your car is, in fact, available on the free market for anyone to buy. The tool is pretty simple to use; it plugs into the car and spits out a code. You’ll have to look up the code for your particular car to see what it means. From there, having identified the issue, you can buy the proper parts and fix it yourself. If you have a bit of knowledge about a car, having your own diagnostic tool can save you from ever having to bring your car into the shop. On the other hand, it’s possible that even if you are able diagnose the issue, the problem will be beyond your capability to fix, and you’ll have to take it in any way. Furthermore, if you don’t expect to need to check cars very often, then you might not want to invest in a several hundred dollar code reader. If that’s the case, there’s always option #3.

Option #3: Go to an Auto Parts Store

Nearly every auto parts store will have a code reader that they can use on your car to determine the issue. This isn’t altruism, it’s business; if a store is able to help you diagnose an issue, then you will be more likely to buy the parts you need to fix it from their store. Aside from who owns the code reader, option #3 is identical to option #2.

No matter which path you choose, it is always important to remain vigilant when it comes to check engine lights. As stated before, you don’t need to panic when it comes on, but you do need to take it seriously. It probably isn’t an important issue, but it might be, and even the smallest problem can become significant if it’s given enough time to grow.


  1. Dough Roller – What to do When Your Check Engine Light Comes On
  2. 20 Something Finance – The Service Engine Light – Your Mechanic’s Dirty Little Secret
  3. Consumer Reports – What Does Check Engine Light Mean