Code Reader Vs. Scan Tool

The Difference Between Code Readers and Scan Tools

scan tool or code reader
There's a world of difference between the scan tools used by professionals and the code readers you can rent or borrow from a local parts store. Hero Images

Question: What’s the difference between a code reader and a scan tool?

I’ve been around cars since I was a kid, but all of this computer stuff is completely foreign to me. I picked up a cheap “code reader” a little while ago so I could start working on my own stuff again, but I don’t think it’s capable of doing what I need it to do. What’s the difference between a code reader and a scan tool, anyway? Which one is better, and which one should I have bought?


There aren’t any hard and fast rules as to what constitutes a basic car code reader and what qualifies as a scan tool, but there are a few things that typically set these devices apart. Both devices feature basic code reading and clearing functionality, but that’s often where a code reader’s feature set ends. Scan tools, on the other hand, may include advanced data reading and playback features, extensive knowledge bases and diagnostic procedures, and even built-in testing equipment.

As to whether you need a code reader or a scan tool, neither device is necessarily “better” than the other. Code readers are cheap and easy to use, and if all you need to do is read and clear codes, then an inexpensive code reader is a great tool to have.

Some really affordable code readers even provide basic access to the full range of parameter IDs (PIDs) that your car’s onboard computer provides, and that can be powerful information if you know what to do with it.

However, a good scan tool is always going to be a much more useful tool in the right hands. Scan tools are more expensive, but they can do everything a code reader can do and then some. Of course, you might also want to consider going with a low-cost option like an ELM327 scan tool if you already have a compatible device that you can use with it.

Code Readers Vs. Scan Tools

Code readers are the most basic computer diagnostic tools that you’ll find, and they provide a pretty basic way of interacting with your car’s onboard computer. If you only need to read and clear codes, then a code reader will do the trick.

Of course, a lot of parts stores and shops will actually check and clear your codes for free, so a lot of folks who would do fine with a bargain basement code reader would actually be better off looking into that sort of service.

Typical Code Reader Features

No two code readers are exactly alike, and feature sets can differ from one model to another. In general, there are some things every code reader can do, other functions that you should be on the lookout for, and a lot of stuff that no inexpensive code reader will be able to handle.

Things a code reader can do.

  • Read and display codes.
  • ​Clear codes and reset the check engine light.

Things a code reader may be able to do:

  • Display trouble code names.
  • Read and display live data.
  • Display freeze frame data.
  • Display readiness monitor status.
  • Reset readiness monitors.

Things you can’t do with a basic code reader:

  • Provide troubleshooting information or tips.
  • Record and play back live data.
  • Graph data or graph specific PIDs.
  • Read manufacturer or pending codes.
  • Utilize functions that require bi-directional communication.

Different scan tools also provide a wildly varying set of features depending on whether you’re dealing with consumer- or professional-grade equipment. Like code readers, scan tools allow you to read and clear codes.

However, even low-end, consumer-grade scan tools include information like code definitions and some type of basic troubleshooting tips. Higher-end scan tools include much more in-depth diagnostic and troubleshooting procedures, and some of them even have built-in testing equipment like scopes and multi-meters.

Limitations of Basic Code Readers

If you buy a code reader and feel like it “isn’t doing what you need it to do,” then you probably ended up with a bare bones device that is literally nothing more than the dictionary definition of code reader. If you need to read anything but generic, hard-set codes, or do anything but read and clear codes, then that type of device definitely isn’t going to do the trick. However, a mid-range device that can read and display PIDs and freeze-frame data may fit your needs just fine.

Code Readers Vs. Scan Tools Vs. ELM327 Dongles

Another option that may be worth exploring is a type of “scan tool” that actually functions as an interface between your car’s onboard computer and another device, like a smartphone, tablet, or laptop. These are typically referred to as ELM327 scan tools, but they can actually function as anything from a very basic code reader, to an advanced scan tool, to the core of a DIY infotainment system depending on the software you use.

Do You Need a Car Code Reader or Code Scan Tool?

Whether or not you actually need a code reader, scan tool, or none of the above, depends on the type and frequency of work that you're doing. Professional automotive technicians typically require high quality scan tools to work efficiently, while the average do-it-yourselfer should be able to get by with a basic code reader, or nothing at all.

If you prefer, or need, to work on your own car, then the type of scanner or reader to get is really a function of how much money you want to spend, and how much money, or time, that purchase will actually save you.

Spending a lot of money on a decent consumer-grade scan tool certainly makes more sense if you own a small fleet of vehicles, while others should be able to get by with the free code reading service offered by a local parts store, and an Internet search to find out what their trouble codes actually mean.