It would be hard-pressed for a modern auto repair shop to consider turning their open sign on without having a scan tool. Most shops have several scan tools at their disposal and often keep investing in more every couple of years. While the do-it-yourself market can usually get by with a basic code and data reader, a professional shop needs a tool that goes far beyond those capabilities.

Scan Tool Capability Analysis
It stands to reason that with all the changing technology the automotive industry is facing each passing year, scan tools need to be able to talk to all modules, have the ability to scan codes and interpret PIDS from those modules, perform bi-directional tests, program or code various modules, and have the ability to graph pids when needed. These capabilities have become the new baseline when shopping for a new scan tool. What separates an excellent scan tool from a lesser featured one now is its ability to provide other functionality for a technician to make their jobs easier and more efficient. Tests like performing topology mapping, fuel trim mapping, volumetric efficiency calculations, catalyst monitor efficiency calculations, interfacing with secure gateways, providing guided diagnostics, built-in scoping capabilities, and having the ability to emulate the OEM scan tools in ways that older scan tools couldn’t have all become what a technician/shop owner is now looking for their next devices to be able to do.

Scan tools have always been classified into three groups; the code and data reader for generic OBD II, the aftermarket scan tool, and the OEM tools. The OEM tools can arguably do the most for vehicle diagnostic procedures, but there is a high expense associated with this equipment classification. Unless one can justify the initial cost with their shop’s car counts, it may not be the
best choice.

Scan Tool Tests and Features
It is often said that most generic scan tools can usually diagnose a drivability related issue by looking at the 6-main inputs. However, we all realize that we face more than just drivability related issues coming into our shops. These are the types of jobs where some of the other types of tools shine. This article could turn into a novel if we discussed all the reasons and tests available on modern devices, so we will focus on a few of the various scan tool features with you today.

One exciting feature some of the aftermarket tools are starting to provide is called topology mapping. The Chrysler tools have been doing this for a while now, but when an aftermarket tool provides us with this feature, we can simplify data bus network diagnostics on several makes and models. Topology mapping provides us with a schematic picture of the various modules on the vehicle’s network. Whether they are nodes or sub-nodes, mapping quickly allows us to see if all modules are communicating and if any of them have set trouble codes. This information can quickly and easily be used by a technician to determine the chain of command on the network, why a module isn’t communicating, where the communications have failed, and what modules may have codes to diagnose the network. We can even have color-coding, which represents further enhanced diagnostics of the network. There are other benefits to this feature as well. A sample of topology mapping from an Autel tool is shown below.

Another series of tests gaining momentum amongst aftermarket tool companies includes tests for volumetric efficiency, fuel trim mapping, catalyst efficiency testing, and relative compression testing. While these tests may be new to some, we were often forced to go to the internet for a calculator of some sort to achieve the base line results after plugging in various information about the vehicle we were working on and multiple lines of data stream pids. Today’s tools are starting to negate the need to leave the driver seat to get these results and give us this information right on our scan tool screens when referring to driver’s seat diagnostics. Imagine a typical complaint of a rough running or misfiring engine. We all know the three things that can cause this type of complaint: an ignition issue, a fuel issue, or the engine’s ability to breathe. We all have learned a series of tests we can perform on these systems to get to the root cause, but often, a lot of time is wasted determining which of these areas we should look for our problem. With the tests listed above, a technician should know which system the problem lies before even opening the vehicle’s hood by merely interpreting the test results that his/her scan tool provides for them.

If you would like more information on these or any other diagnostic related tests, be on the lookout for a more advanced course coming soon at While you’re there, check out the extensive video training collection available.