By Larry Carley c2007
Ordinary scan tools for reading engine fault codes are not any help on antilock brake systems. It takes special software to access the ABS diagnostics, which means using a factory scan tool, a high end professional scan tool, or one of the new dedicated ABS tester scan tools.
A scan tool that can read ABS codes can help you identify faults to figure out why the ABS warning light is on, but a code by itself does not tell you which part needs to be replaced. Further testing is usually needed to isolate and identify the fault that is causing the problem.
What's more, intermittent problems may not set a fault code. So if there is no code, you cannot assume everything is fine. You have to check the operation of the system as well as individual components to figure out what is wrong.
Factory scan tools and high end professional scan tools have bi-directional capability that allows them to run various ABS system self-tests to help detect faults. The scan tool may also cycle the ABS solenoids to make bleeding the brakes easier. Most entry level ABS scan tools have little or no bi-directional capability and cannot run these tests.
Point by point resistance and voltage checks can help you isolate problems with or without codes, but such tests can be very time-consuming and may not always reveal a problem. Dynamic tests are also impossible with this approach because you have no means of exercising or testing the operation of the ABS solenoids and valves. Such components may show the correct voltage and resistance readings, but may not be functioning correctly. So some means of testing their function may be necessary for an accurate diagnosis. That is where a bi-directional scan tool or dedicated ABS tester can make a big difference.
At the fall 2007 AAPEX show in Las Vegas, Actron introduced this brand new ABS BrakeScan tool. This is the first affordable tool for basic ABS diagnostic work. The tool sells for under $300, and is a great product for the do-it-yourselfer or for bgasic ABS diagnosis by a professional technician. The tool covers 1996 and newer domestic cars (GM, Ford & Chrysler), and plugs into the OBD II connector under the dash. It reads all ABS codes for these applications, displays code definitions, and can be updated with future applications online.
The OTC 3762 is a 3-in-1 scan tool that does ABS and Airbag codes, as well as OBD II engine codes. This tool is designed for professional technicians and body shops, and sells for around $1500. It covers all 1996 to current Vehicles including most Audi, Chrysler, Ford, GM, Honda, Isuzu, Jeep, Mazda, Nissan, Saturn, Toyota and VW models.
The tool displays codes, code descriptions, and data stream for most 1987 and newer ABS systems and vehicles. You can display data values and perform bi-directional tests on many ABS applications, including GM Delco IV and Delco III. That means you can activate solenoids, relays, and motors to verify proper operation.
The Air Bag/ABS scan tool also allows bi-directional testing and brake bleeding to further enhance your diagnostic capabilities. These include motor rehome test, manual and hydraulic control test, EMB test and motor test, gear tension relief, enable relay test, voltage load test, lamp test, system ID test and brake bleed.
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