Thinking about buying a new scan tool? Choosing a tool that provides the best coverage and the most diagnostic bang for your buck isn’t easy with so many different products to choose from today. There are simple code reader tools, entry-level “generic” scan tools, professional-grade tools with bi-directional communication and additional test capabilities, OEM scan tools, and all kinds of software for transforming a laptop computer, desktop PC or Personal Digital Assistant (PDA) into a diagnostic scanner.

If you’re a first-time scan tool buyer, the tool that will probably work best for you is a professional-grade “all makes and models” aftermarket scan tool — unless you specialize in only one particular make, in which case you may want to buy the corresponding OEM scan tool.

If you’re replacing an older, outdated scan tool, or want a tool that provides better import coverage or or a multi-function scan tool that has additional features such as the ability to graph and display waveforms, to analyze exhaust emissions, etc., then you’re probably looking at a high-end aftermarket combination scanner with all the bells and whistles.

Truth is, most import specialists don’t rely on a single scan tool for everything. They own multiple scan tools, and often use different scan tools for different purposes. So with that in mind, let’s look at some of the products that are available and what they do.

BASIC CODE READER
Code readers are relatively inexpensive (typically less than $100) and can be used to quickly find out why a Malfunction Indicator Lamp (MIL) is on. Just plug the tool into the vehicle’s diagnostic connector and read any diagnostic trouble codes (DTCs) that have been set. It won’t tell you what parts need to be replaced, but it will give you some diagnostic direction so you can tell a customer why his/her MIL lamp is on, and what type of repairs might be needed.

Most code readers are “generic” and will read global OBD II codes on all 1996 and newer vehicles. There are also some pre-OBD II code readers and a few vehicle-specific code readers. The least expensive models typically display only a code number and do not provide a code definition. You have to look up the code definition in a manual or on your PC if the tool comes with a list of codes on a CD. If there’s no manual or CD with the product, you may have to search online for a definition.

The better code readers provide both a code number and a definition. Many also display the readiness status of the vehicle’s OBD II monitors. This is good information to have because it tells you whether or not the monitors have run. When a fault occurs, it may prevent some monitors from running (like the catalytic converter monitor if an oxygen sensor code is present). The OBD II monitor status will also tell you if the vehicle is ready for an emissions test or is capable of passing an OBD II plug-in emissions test. Depending on the model year, the vehicle may be rejected if more than one monitor has not been completed.

The limitation of a code reader is that it’s not a scan tool. It can’t display or capture sensor data or run diagnostic tests. It can only read and clear fault codes, and possibly display OBD II monitor readiness status. That’s it. For advanced diagnostic work, you need a professional-grade scan tool.

ENTRY-LEVEL SCAN TOOLS
For import applications, entry-level scan tools typically provide only generic OBD II codes and little or no “enhanced” OBD II data. The software in most of these scan tools is also limited to powertrain only, so you can’t access ABS codes, airbag codes, climate control codes, or body or chassis codes. The list of Parameter Identification Data (PIDs) displayed may also be very limited and may not include much of the data that an OEM scan tool or professional-grade scan tool can display.

PROFESSIONAL-GRADE SCAN TOOLS
Professional-grade scan tools are designed for working professionals, not DIYers. These are the workhorse scan tools that are necessary for advanced diagnostics and troubleshooting. Prices typically start around $500 and go up to $2,500 or more depending on the model and features. Some multi-function scan tools that combine scope and exhaust analysis features can cost upward of $7,000 or more.

Their bi-directional communications capability allows the tool to access and run system tests and actuator tests that are accessible through the PCM, which can be very helpful when diagnosing ignition, fuel system and emissions problems, and may be required when working on various ABS systems.

For example, if the MIL light is on and the DTC indicates an EVAP leak, you can use the scan tool to open and close the EVAP canister purge valve and tank vent valve while using a smoke machine to find the leak. Or, on a vehicle with ABS, you can use the scan tool to cycle the ABS solenoids while bleeding the brake lines.

The software or cartridges that come with some professional-grade scan tools can also provide additional time-saving diagnostic help. The software may list possible causes of a fault, additional tests that should be done to isolate a fault, or suggest other steps that may be necessary to fix a particular problem (such as reflashing the PCM — which requires a scan tool that is J2534 compliant or a separate flash tool).

Some say many aftermarket scan tools lack the depth of an OEM scan tool as far as the number of PIDs that can be displayed and the tests that can be performed. But the main advantage of an aftermarket scan tool is that it displays all available data in the same format for every make and model. You don’t have to learn and remember different menus and entry procedures for different OEM scan tools.

Historically, the software that’s been developed for aftermarket scan tools has focused primarily on North American domestic applications. When import coverage is included or is available as an add-on cartridge or software upgrade, the coverage may be limited to Honda, Mazda, Mitsubishi, Nissan, Toyota, etc. Some makes may have limited coverage or no coverage at all, especially for the European makes.

On the other hand, there are also aftermarket scan tools that provide excellent coverage on selected European or Asian models. Many of these tools come from companies that sell scan tools abroad and have a working relationship with the European or Asian OEMs. Several such aftermarket scan tools provide almost the exact same software features as the OEM dealer scan tools.

Many aftermarket scan tool suppliers sell more than one model or version of their professional-grade scan tools, so buyers can choose a product that best suits their needs and budget.

OEM SCAN TOOLS
You might think the best scan tool for an import specialist would be an OEM dealer scan tool. The OEM scan tool can access all the information that the vehicle is capable of providing (whether you actually need it or not), including powertrain, airbag, antilock brakes, climate control, body and chassis electronics. On the surface this sounds great, but OEM scan tools are designed for OEM dealerships, not aftermarket independent repair shops. Consequently, some of the PIDs and self-tests that can be accessed with the OEM tool rely on supplemental information from the OEM service manual or database. If you don’t have the accompanying diagnostic procedures, test specifications and/or charts, the OEM tool may be more confusing than helpful in steering you toward a correct diagnosis. Some OEMs also “decontent” certain software features from the aftermarket versions of their scan tools. Honda, for example, removes the ability to access the anti-theft system from its aftermarket scan tool software.

OEM scan tools are also limited to one particular make of vehicle, and some cover only certain model years. But what if you also work on other makes? The OEM scan tool may have “global” OBD II capabilities, but the information that it displays on other makes and models will typically be limited and probably not include any of the “enhanced” codes, PIDs or tests you may need. OEM scan tools are also expensive (typically $2,000 or more) and, as we said earlier, some aftermarket versions are “decontented” to remove certain features that are considered “dealer-only” exclusives (like the ability to access anti-theft systems for reprogramming ignition keys and modules, or the ability to flash program PCMs).

Another thing to keep in mind with OEM scan tools is that they are all different. Different OEM scan tools use different menus, organize their information differently, and use different buttons and sequences to access and display information. In addition, DTCs and PIDs may be displayed differently. Some can graph sensor data and display waveforms, but many do not — which means you need a separate scope to do this kind of diagnostic work.

SCAN TOOL OBSOLESCENCE
The fact is, scan tool obsolescence is a fact of life. The latest generation of OEM and aftermarket scan tools are moving away from replaceable hardware update cartridges and use flash memories that can be easily updated by downloading new software over the Internet or from a tool truck vendor. It’s a faster, better and generally less expensive way to keep your equipment current, but it’s no guarantee that your tool may not be obsolete within a few years, depending on what kind of new technology the vehicle manufacturers introduce.

Any new scan tool that you buy today should be Controller Area Network (CAN) compliant. CAN is a multiplexing system that allows numerous modules and systems to share information over a common data bus. CAN, which will be required on all new cars by 2008, allows faster communication and requires special scan tool hardware and software to handle the various CAN communication protocols.

If you need a scan tool that is backward compatible with older pre-OBD II vehicles, you can usually get that in a professional-grade aftermarket scan tool. But some OEM scan tools are not backward compatible. One alternative is to buy an older, used scan tool on eBay, or similar website, for the older vehicles you service.

SOFTWARE-BASED SCAN TOOLS
The advantage here is that, in most instances, you are not buying hardware, just the software to access the vehicle’s onboard diagnostics. Of course, you also need an interface cable (USB or serial) to connect your PC, laptop or PDA to the vehicle’s diagnostic connector.

The price for this kind of software typically starts around $300 and goes up depending on its capabilities and features. The most basic programs allow you to read and clear codes, check OBD II monitor status and read basic sensor data. The more advanced software can chart and graph waveforms, display up to nine separate parameters as digital displays, bar graphs or meters, record and play back freeze-frame data, and do various bi-directional tests and control functions.

One of the advantages of buying software that converts a PC, laptop PDA into a scan tool is speed (if your equipment has a fast processor and lots of memory). And, with both laptop and desktop PCs, you can simultaneously display a lot of different PIDs, graphs and other information thanks to the large color screen display.

Some companies also sell software that can convert a PC into a powerful, high-resolution oscilloscope for viewing ignition patterns, sensor waveforms, you-name-it. The software may even include a reference library of good and bad waveforms to help spot problems that might otherwise escape notice.

Another important consideration when shopping and comparing scan tools is technical support. The best advice here is to talk to others who use a particular brand of scan tool and ask them how they rate their technical support experiences.

Has the tool been reliable and trouble-free?

How difficult (and expensive) is it to upgrade the tool?

If there’s a problem with the tool, who handles the warranty repairs?

Were any problems resolved quickly and painlessly?