Code Readers vs. Scan Tools

Both can read car codes, but which is best for which situation?

Both code readers and scan tools are designed to interface with a car's on-board computer or diagnostic system to help identify or troubleshoot problems.

Generally speaking, a code reader is a simplified version of a scan tool, only capable of performing basic scans of trouble codes. A scan tool can read and clear trouble codes, but it may also be able to provide advanced data reading and playback features, knowledge bases, diagnostic procedures, and built-in testing equipment.

Code Reader vs scan tool

Overall Findings

Code Readers
  • Read, display, and clear car trouble codes.

  • Reset the check engine light.

  • More advanced or expensive code readers can read and display data, reset readiness monitors, or access parameter IDs (PIDs) provided by the onboard computer.

Scan Tools
  • Read pending, generic, and manufacturer-specific codes.

  • Provide troubleshooting information, tips, and trouble code definitions.

  • Record and play back live data.

  • Graph data or access specific parameter IDs (PIDs).

  • More advanced scan tools include diagnostic equipment like scopes and multimeters.

Do You Need a Code Reader or a Scan Tool?

Because they're cheap and easy to use, code readers are convenient for car owners and mechanics simply looking to read and clear some diagnostic codes. Scan tools are more expensive, but they can do everything a code reader can do, as well as provide troubleshooting tips, data readouts, and diagnostic equipment.

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 cheap code reader or a nearby service willing to read codes for free.

If budget is your priority, consider taking your codes to an auto parts store or shop, as many will check and clear codes free of charge.

Spending a lot of money on a decent consumer-grade scan tool makes sense if you're a car enthusiast with a small fleet of vehicles, but most people can get by with the free code reading service offered by a local parts store, or an internet search to find out what their trouble codes mean.

Code Reader Features

No two code readers are the same, with feature sets depending largely on price. Any code reader will be able to read, display, and clear codes, and reset the check engine light. More advanced code readers can do the following:

  • Display trouble code names
  • Read and display live data
  • Display freeze frame data
  • Display readiness monitor status
  • Reset readiness monitors
  • Some code readers provide basic access to the full range of parameter IDs (PIDs) provided by a vehicle's onboard computer provides.

Scan Tool Features

Scan tools typically offer a suite of features depending on budget and intended use. Low-end, consumer-grade scan tools provide code definitions and basic troubleshooting tips. High-end scan tools include more in-depth diagnostic and troubleshooting procedures, and some have built-in testing equipment like scopes and multimeters.

Here are some of the things a scan tool can do:

  • Provide troubleshooting information or tips
  • Record and playback live data
  • Graph data or graph specific PIDs
  • Read manufacturer or pending codes
  • Utilize functions that require bidirectional communication

Another option to consider is an ELM327 scan tool. These microcontrollers function as an interface between your car’s onboard computer and a personal computer, which could be a smartphone, tablet, or laptop. They can perform the duties of a basic code reader or an advanced scan tool.