Personal Finance

What To Do When Your Check Engine Light Comes On

When your check engine light comes on you don't always have to go to a mechanic. Here are your options.

We recently bought a car for our kids to drive. It’s a beauty, too. We’re talking a 2004 Mercury Sable with 170,000 miles. And after just a few short weeks of ownership, the dreaded “check engine light” came on.

Now we did what most probably do–we took it to a repair shop. I learned a few things from the experience. One was never to go back to AAA Service Station (see below). Based on my costly experience, here’s what to do when your check engine light illuminates.

The Dreaded Light

First, let’s talk about what the light actually means. The computer in your car that triggers the check engine light is monitoring the efficiency of your car and the emissions. When the light comes on, it doesn’t necessarily mean you have to stop the car immediately. But you do need to determine what the problem is as soon as possible. If the check engine light is on in conjunction with the low oil or high-temperature light, however, there may be more serious problems with your car that should be addressed immediately.

In my experience, the check engine light usually indicates a small problem that needs to be addressed before it becomes a larger (and more expensive) problem. Continuous driving with the check engine light usually means you are experiencing reduced fuel mileage and reduced performance. The check engine light can indicate something as simple as a loose gas cap or something more severe such as a bad sensor or excessive exhaust. We see the light a lot on our Honda Odyssey, and every time it’s because we haven’t screwed the gas cap on tight enough.

So now that you know something is wrong, what do you do? You have a few options.

Go To A Mechanic

One option is to take it to a mechanic for a diagnostic test. A mechanic will plug your car into a meter that will give him a list of trouble codes that were logged when the check engine light came on. These codes will tell the mechanic what the problem is. Before you head out to a mechanic, however, there are a few things to consider.

First, before you even go to a mechanic, make sure you ask what the charge is for the diagnostic test. Second, if there is a charge, then ask if the fee is credited towards the repair bill. I assumed my diagnostic test fee would be credited towards the bill as long as I had them do the repairs. It turns out that AAA service shops don’t work that way. As a result, I paid $150 for diagnostic tests that took them about 10 minutes to complete.

Of course, I won’t be going back to an AAA shop. There are plenty of mechanics in my area that don’t charge anything for a simple diagnostic test. If mechanics near you do charge, make sure the fee is credited to the future cost of repairs. If not, go to a different mechanic.

Purchase A Diagnostic Tool

If you are more of a do-it-yourselfer, you can purchase a code reader online or in most auto parts stores. The reader works just like the diagnostic tool used by mechanics. You plug it into your car (usually located under the dash on the driver’s side) and it will retrieve the error codes. Some of the tools show you the error codes on their display and provide a book to translate the codes. Others require you to plug the tool into your PC and software will interpret the codes for you.

The code readers can range anywhere from $25 – $300 and can easily be found on Amazon. There is even an iPhone app called the goPoint Technology GL1 OBD-II Accessory for iPhone (also works with iPod and iPad) that can tell you why your check engine light is on. If you are able to do the repair work, a code reader can pay for itself quickly.

Visit An Auto Parts Store

Another option would be to take your vehicle to an auto parts store and have them plug in a code reader. Many stores provide this service for free in hopes that you will purchase the parts you need to make the repair. If the repair requires special tools, they will often rent those to you for a very small fee (and some will return the rental fee when you return the tool). Some stores are even able to give you directions or diagrams to help you complete the repair.

Rob Berger

Rob Berger

Rob Berger is the founder of Dough Roller and the Dough Roller Money Podcast. A former securities law attorney and Forbes deputy editor, Rob is the author of the book Retire Before Mom and Dad. He educates independent investors on his YouTube channel and at

Recommended Stories