Tech Update: Scan Tools & Code Readers – UnderhoodService

Tech Update: Scan Tools & Code Readers

One thing you can always count on in the automotive repair business is that diagnostic equipment is constantly changing. It must to keep pace with changing automotive technology. So the latest crop of scan tools and code readers have more features, more capabilities and give you more bang for your buck than ever before.

There’s a world of difference between a low-cost basic code reader and a full-fledged scan tool. A basic code reader is relatively inexpensive and is handy for reading diagnostic trouble codes (DTCs), checking the readiness status of OBD II monitors and clearing codes. 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 provides 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 than 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.

And if you want to work on the newest vehicles that have a Controller Area Network (CAN) computer system, you need a scan tool that is CAN-compliant.

CAN is a high-speed data link that runs 50 times faster than the four existing OBD II communication protocols (J1850-PWM, J1850-VPW, ISO-9141 and ISO-14230). The CAN protocol provides more information and at a faster rate for better communication between onboard electronics and external diagnostic equipment. Some older scan tools that were manufactured before CAN came along don’t have the necessary hardware to read the faster data, and may not be upgradeable. CAN is required on all new vehicles this year, so if you’re shopping for a new scan tool, make sure it’s CAN-compliant.

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. For more information about the OEM service information websites and access fees, visit

What Do You Really Need?
Some higher end scan tools not only display codes and data, but also graphs of sensor waveforms. The ability to graph data makes it easier to see what is actually going on, and to compare data. For example, if you are troubleshooting a rich or lean fuel condition, you might want to look at oxygen sensor data, throttle position data and short-term fuel trim data simultaneously.

That brings us to another very important point with respect to scan tools and the usage thereof. Many technicians never fully utilize all the capabilities that are included in a high-end scan tool. Learning how to use all of the features takes time, and learning which features are the most helpful takes time and experience. You don’t just pick up a scan tool and start fixing cars. Anybody can plug a scan tool into a vehicle and pull codes or scroll through data displays. But if you don’t know what the numbers mean or how to use the information the tool is capable of displaying, the scan tool data isn’t much use.

The bottom line here is make sure you’re “scan tool ready” before you make a major purchasing decision. For starters, it helps to be ASE certified in Advanced Engine Performance.

The Advanced Engine Performance Specialist (L1) Test consists of questions that test a technician’s knowledge of computer-controlled engine systems. In addition, the test measures the technician’s ability to diagnose the causes of high-emissions failures. This is especially important in areas with basic I/M (inspection/maintenance) and enhanced I/M (ASM or I/M240) programs.

If you can pass the ASE L1 test, you should be competent enough to use most of the functions in a professional-level scan tool. Actually, you don’t have to be L1 certified to buy or operate a scan tool, but you do need the knowledge and skills at that level to make the most of this kind of diagnostic equipment. At the very least, you have to understand the basics of computerized engine management systems, what the basic sensors are and how they operate, what OBD II monitors, what OBD II readiness status is, how to read wiring diagrams, how to use a DVOM (digital volt ohmmeter) to perform basic circuit checks, read voltages and resistance, etc. If you are not at this level, then seek out additional training from a local community college, training clinics or online training.

Scan Tool Trends
In recent years, more and more new diagnostic tools have been introduced into the aftermarket.

The increased competition is driving down prices and forcing scan tool suppliers to include more features at no extra cost. This includes larger displays, color graphics, broader vehicle make and model applications, and more “PIDS” (parameter identification data). Some new scan tools now include domestic ABS, airbag and transmission coverage as part of its diagnostic package. As time goes on, hopefully aftermarket scan tool manufacturers will add more “dealer only” capabilities to their products so their scan tools can also communicate and interact with other onboard electronics that are currently accessible only through a factory scan tool. These systems include HVAC controls, onboard navigation, communication and entertainment systems, electronic steering and suspension systems, body control modules for power windows, doors and sunroofs, anti-theft systems and tire pressure monitoring (TPMS) systems.

Menus have improved, making the tools easier to use. The larger screens and color graphics also make it easier to see the data even in bright sunlight (a feature that was sorely lacking on some older scan tools). Good visibility reduces the risk of misreading information, and is a plus for aging technicians whose eyes may not be as sharp as they once were.

Many technicians and service writers today are also using a simple code reader to perform a preliminary diagnosis (because these tools are so quick and easy to use). This often allows the technician or service writer to give the customer a better idea of what might be wrong and what it might cost to fix their problem. In other words, they are using the code reader to help sell the repair. When the customer gives the go-ahead, they then get out their professional-level scan tool to do the additional diagnostics.

Finally, there is the question of obsolescence. Most scan tools today are upgradeable with some type of plug-in cartridge or memory card, or can be flash reprogrammed by downloading new software from the equipment supplier via the Internet or from their local sales representative (the guy in the tool truck). The main issue here is cost. Annual updates are a must to stay current with the latest vehicle diagnostics, so there’s no way to avoid them.

The bottom line here is shop carefully, compare features and ask A LOT of questions before you decide on a scan tool. Buying a tool that is difficult to learn or use, lacks some of the features you may need to fix certain kinds of problems (like flash reprogramming PCMs), or retains little resale value (to help offset your next scan tool purchase) is an investment mistake you want to avoid. Talk to other technicians to find out what kind of scan tool they are using, what they like and don’t like and then make your buying decision.

Just remember, a scan tool is supposed to help you make money. The only way it can do that is if it does everything you expect it to do.

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