Where can you get Free Check Engine Light Diagnosis?

Check Engine is one of the indicator lights in the instrument panel and also a part of On-Board Diagnostic system aka OBDII. When there is something wrong in the engine or emission system, the vehicles computer turns on the Check Engine Light to notify the driver. At the same time, the vehicle computer stores the code(s). You can see the codes by scanning the vehicle computer with a scan tool (also called a scanner or code reader.) Scanning the computer is the first step of check engine light diagnosis. And you can get free check engine light diagnosis in some ways

image of check engine light

Auto Parts Stores

Here is a list of auto parts stores that offer a free computer scan and tell you the codes. These are not all stores but my local stores I verified.

  • Advance Auto Parts
  • AutoZone
  • Napa Auto Parts
  • O’Reilly Auto Parts
  • Pep Boys Auto Parts

The reason why they do it for free is that it’s not technical job. What they do is to plug a scanner into an OBD port and press a few buttons, and they get the codes.

But still, why do they do that for free?

First of all, they are not repair shops but parts stores. I guess they are hoping you to buy the parts at their stores to fix the check engine light problems for yourself. They may even mention the common causes of the problems of the specific code. For example, the code P0136 is O2 Sensor Circuit Malfunction Bank 1 Sensor 2. A store clerk may mention that a bad oxygen sensor can be the cause. Sometimes, it’s true, but not always. Keep in mind that you can’t assume the cause of the problem without further diagnosis.

Local Mechanic Garage

If you have a good relationship with your local mechanic, they may scan the computer for you for free. But that’s all they offer for free. Unlike parts stores, mechanic garages fix the problem. They are capable of identifying the cause of the problem with further diagnosis. This diagnosis incurs a fee for labor of at least an hour. So, if you go to a mechanic garage, tell them that all you need is to have the computer scanned, and make sure if they do that for free in advance.

Scan for yourself

It’s not exactly free because you have to buy a scan tool, but it’s recommended for a DIYer. The prices of scan tools range from $20 to thousands of dollars. You can get a decent one for around $50. Once you bought one, you can scan the computer as many times as you need. You can freely use other features like clearing the check engine light, I/M readiness monitor, live data, and so on. BlueDriver is one of the most popular scan tools. Unlike conventional scan tools, BlueDriver is a Bluetooth adapter that connects with your smartphone and works with the app. It has advanced features like enhanced diagnosis (ABS, SRS, TPMS, etc.), Mode 6, Repair Report, and so on. Click here to see the details of BlueDriver.


Scanning the computer and getting the codes are the first step of tackling with check engine light diagnosis. With the codes, you can look up the details, possible causes, and possible fixes on the internet. In the end, you may still have to go to a mechanic garage to fix the problem, but it’s good to have some insight about the problem beforehand. If they tell you something unrelated to your research, you should ask for more details about that. You also have an option to go to another mechanic garage for a second opinion.

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