Scan Tools: Scan Tools Offer a Window Into a Vehicle’s Inner Workings

Scan Tools: Scan Tools Offer a Window Into a Vehicle’s Inner Workings

Scan Tools Offer a Window Into a Vehicle’s Inner Workings

Larry Carley, Technical Editor
[email protected]

Technicians who attempt to make driveability or emissions repairs today without a scan tool are troubleshooting in the dark. A scan tool is absolutely essential because it provides a window into the inner workings of the engine management and onboard diagnostic system. The tool allows you to read fault codes that have been set, to see the data the powertrain control module (PCM) is receiving from its sensors, and to see the commands the PCM is sending out. The tool can also tell you if all of the onboard diagnostic monitors (self-checks) have run, and whether any faults were found. Higher end scan tools with bi-directional capability also give you the ability to command various test functions so you can see if the components respond they way they should. Without this kind of diagnostic firepower, it’s easy to reach the wrong conclusions and to replace the wrong parts — and to lose business because you can’t fix your customers’ problems.

Much More Than Codes
Some entry-level technicians think all they need to fix cars is a basic code reader. Code readers are quick, easy-to-use and relatively inexpensive (typically under $100), and are handy for finding out why the check engine light (malfunction indicator lamp) is on. You just plug the tool into the 16-pin diagnostic connector under the dash, turn on the ignition and read the codes.

You can even push a button to erase the codes so the check engine light will go out. But that doesn’t fix the problem that caused the light to come on. And a code by itself will never tell you which part needs to be replaced (or why). A code is just a starting point for further diagnostics. That’s why every professional technician who does driveability and emissions repairs needs a full-fledged scan tool that can:

• Read OEM vehicle-specific P1 “enhanced” codes as well as basic or “generic” P0 codes.

• Read live system data including sensor outputs, various PCM command outputs and other useful PIDs (parameter information data). Many vehicles today have several hundred PIDs that can be displayed on a scan tool — if the tool will read them.

• Read stored “freeze-frame” data that is captured when codes are set.

• Run bi-directional “key on engine off” (KOEO) or “key on engine running” (KOER) commands and self-tests to check system response.

The better scan tools can do even more. Some have software that allows them to run cylinder balance tests and other specialized tests that are unique to that particular tool. Some tools also have software that provide diagnostic guidance (now what do I do?), and even references technical service bulletins for solving difficult problems.

Other scan tool add-ons include such goodies as the ability to graph data or display sensor waveforms (graphing multimeter or digital storage oscilloscope). A multi-channel scope capability is a very useful feature because a scope can capture and display data at a faster rate that what comes through the diagnostic connector. A scope requires some additional hookups, but really opens the diagnostic window even wider for a better view of what’s going on.

Another add-on is a 4- or 5-gas infrared exhaust analyzer. This can show actual exhaust gas readings to confirm emissions compliance or troubleshoot air/fuel mixture or catalytic converter problems.

CAN Compliant
As automotive technology continues to evolve at an ever faster pace, so too must the scan tool technology that is used to fix these vehicles. Starting in model year 2003, a new onboard communications protocol called “CAN” (Controller Area Network) is being used on more and more vehicles. CAN uses a much higher baud rate to allow faster communication between modules. Because of this, CAN vehicles require a scan tool that is CAN-compliant. Some older scan tools are CAN-capable and can be upgraded with new software or hardware cartridges, but others cannot. CAN will be required on all new vehicles by model year 2008. So if you are shopping for a new scan tool, make sure it is CAN-compliant.

Flash Reprogramming
Another feature that is becoming increasingly necessary for repairing late-model vehicles is the ability to flash reprogram PCMs and other modules. Some driveability and emissions problems can only be solved by reflashing the PCM, and this requires a professional-grade scan tool with J2534 “pass-thru” capability, or a separate J2534 flash reprogramming tool.

Reflashing a PCM requires getting the latest PCM flash update from the vehicle manufacturer. The update may come on a CD or be downloaded from the OEM website. The vehicle manufacturers all have websites that provide fairly complete access to all of their current service information for 1996 and newer vehicles, including technical bulletins and PCM flash updates. Some even have online training courses. Most require a subscription fee for access, which typically costs about $20 to $25 for a one- to three-day access, or several hundred dollars a month, or $1,500 or more for a yearly access. For more information about the OEM service information websites and access fees, visit

For flash reprogramming GM applications, you need a Tech 2 scan tool or Vetronix Mastertech. For Ford applications, you need a Ford New Generation Star (NGS) scan tool.

For Chrysler applications, you need a Diagnostic and Reprogramming Tool (DART). Chrysler dealers use the Mopar Diagnostic System (MDS2) and DRB III scan tool.

For import applications, you need the factory scan tool the dealer uses, an aftermarket scan tool with reflash capabilities for that vehicle, or a J2534 pass-through device that will work on the vehicle.

OEM or Aftermarket Scan Tool?
The OEM factory scan tools that dealer technicians use are great because they provide full access to all of the PIDs, codes and self-tests that are available on that make of vehicle. But most factory scan tools do not work on other makes, or if they do they only read generic OBD II codes and limited data.

If a technician spends a lot of time working on a certain make of vehicle, he can probably justify the cost of buying a factory scan tool just for that make. But factory scan tools are expensive, typically costing upwards of $6,000 or more. That makes it very expensive to own a different scan tool for every make of vehicle that might come into your shop for repairs.

Aftermarket scan tools, by comparison, are universal in nature, and typically have the capability to handle most makes and models — with the appropriate cartridges or software and adapter cables. This is a very cost-effective way of providing broad diagnostic coverage at reasonable cost. Some of the higher end aftermarket scan tools cost almost as much or even more than some OEM factory scan tools. But when you consider the versatility of the tool and all the applications it can cover, it’s really a bargain.

All of the current scan tools and scanner software is OBD II-compliant and cover 1996 and newer vehicles. Some are also backwards compatible and cover OBD I vehicles as well (additional adapter cables are usually required).

Aftermarket scan tool manufacturers have packaged their products in such a way as to give technicians a selection of products to suit different needs and budgets. If all you have is $300 or $400 to spend on a scan tool, you can buy a fairly versatile tool that will read most codes, most of the common PIDs and do basic bi-directional tests on domestic makes and a limited range of import makes. For high-end diagnostics, you can spend as much as your budget can handle. Prices for higher end scan tools with advanced capabilities, such as graphing or a multi-channel scope, typically start around $2,000 and go up to $7,000 or more.

Some aftermarket manufacturers also offer scan tools for specific import makes that have virtually the same capabilities as the OEM factory scan tool — and usually at much lower cost.

Which Platform?
The less expensive scan tools are typically small, hand-held devices with a simple black-and-white LCD display and some push buttons on the front. Backlit displays improve readability in poor lighting.

More advanced (and more expensive) scan tools typically have larger color displays, more display lines, a larger box (often a tablet-style format), more inputs and outputs (including volt/ohm multimeter hookups, amp probes and/or scope hookups), and larger flash memories for holding and storing service information and vehicle data. Some also have infrared or Bluetooth capabilities for connecting to a shop computer or printer. Larger, color displays improve readability (especially for older eyes), and allow more PIDs and/or graphs to be displayed on a single page so you don’t waste time scrolling up and down or jumping from one page to another.

PC-based scanner software is also becoming a more popular alternative to a traditional scan tool. The software typically requires Windows 98, XP or Vista, and runs on a desktop or laptop PC. The advantage with this approach is that you only pay for the software, not hardware (except for a cable to link the computer to the vehicle’s diagnostic connector).

The larger format of a PC monitor or laptop screen is more readable than a small LCD screen on a small, hand-held scan tool. And with a wireless or cable modem hookup, the PC or laptop can also provide fingertip access to service information on aftermarket or OEM websites. A laptop is as portable as a tablet-style scan tool, but a desktop PC must either be stationary or placed on a wheeled cart.

One unavoidable cost of owning a scan tool or scanner software is paying for annual updates. The software that operates all scan tools gets out-of-date very quickly. Unless you are running scanner software on a PC or laptop with an Internet connection that automatically downloads updates as soon as they are available, the software that interacts with the vehicle will always be behind the curve almost from the day you buy it.

The software in most aftermarket scan tools typically lags that in the OEM factory tools by a year or two. This is because (1) newer cars are under warranty and usually go back to the dealer for repairs the first two or three years, (2) the OEMs may not release their latest service information to aftermarket scan tool suppliers until some time after the new models are out, and (3) it takes time for the aftermarket scan tool suppliers to review, process and reformat the latest service information for their tools.

Vehicle manufacturers may also release new self-tests or other diagnostic information throughout the year for current or previous model years. These will usually be included in an annual update, but waiting a full year to update your tool or software may be waiting too long. In any event, annual updates are a must to stay current because you don’t know what may have changed from one model year to the next.

The cost of flash updating a scan tool these days typically ranges from $400 to $750 a year depending on the tool and manufacturer. The cost of updates for one year is usually included in the initial purchase price of the tool. But with some, you have to subscribe to annual updates or your tool ceases to function when the initial subscription runs out!

If you own multiple scan tools (say an aftermarket scan tool and one or more OEM factory scan tools), the cost of keeping all of these tools current can really add up fast. And whoever owns the scan tool bears the cost of the updates. If you’re a technician and you own your own scan tool (as most do), the cost of the updates comes out of your pocket. Ideally, your employer should reimburse you for these costs — but few do. If you’re a shop owner and own scan tools for your technicians to use, you have to factor the cost of the annual updates into your overhead and pass the costs along to your customers in the labor rate you charge.

A growing number or shops now charge their customers an “information access fee” if they have to go online to research or download service information from an aftermarket or OEM service information website. The cost of this information should be billed the same as the cost of replacement parts, shop cleaning supplies and waste disposal fees. It’s all a cost of repairing the vehicle.

Learning How To Use
The biggest challenge when buying a new scan tool is learning how to use it effectively. Many technicians never really learn the full diagnostic capabilities of their scan tools because all they use the tool for is to read codes and sensor data. Scan tools with bi-directional capability can run a battery of self-tests to check the operation of various components (including the fuel pump, relays and other devices). The self-tests can be used to verify problems as well as repairs to reduce comebacks.

Most scan tools that cost more than $400 today can also access Mode 06 diagnostic information — if you know where to look for it and how to read and use the hexadecimal codes once you find it (Hint: Mode 06 can be used to diagnose pending faults that have not yet set a code, and to diagnose misfires, EVAP and catalytic converter problems if these monitors have not yet run). The key to getting the most out of any scan tool or scanner software is to attend some advanced OBD II diagnostic training courses — and to learn what some of these tools can do before you have to actually use the tool to fix a customer’s car.

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