AVON, Ohio – The upcoming Commercial Vehicle Safety Alliance’s (CVSA) International Roadcheck inspection program, May 16-18, will include a focus on violations involving antilock braking systems (ABS).
While ABS violations – indicated by warning lights in the cab or on the trailer – are not typically categorized as out-of-service infractions, the technology plays an important role in driver and vehicle safety.
This installment of the Bendix Tech Tips series discusses what to do if you discover an illuminated ABS warning lamp.
The Basics of ABS
Antilock braking systems use wheel speed sensors that indicate to the ABS electronic control unit (ECU) if wheel slip is happening. The ABS system often works with the vehicle’s electronic stability control (ESC) full-stability system, if equipped, to help prevent a tractor or trailer’s wheels from locking up and causing skids on surfaces like ice, wet roads, or loose gravel. ABS is a proven technology, mandatory on most air-braked commercial vehicles manufactured in North America for more than 20 years.
A properly functioning ABS helps the driver maintain control of the vehicle while braking and serves as a foundation for more advanced safety systems like full stability and collision mitigation.
“Checking your ABS lamps for proper functioning should be part of your typical pre- and post-trip inspection,” said Ryan Hurley, vehicle systems engineer at Bendix. “It’s important to note, though, that if your ABS warning lamp does come on while you’re driving, it’s not going to affect standard service brake application: Your truck’s service brakes will still work. ABS, ESC, and collision mitigation technologies, however, may not be fully functional. Keep driving to the next safe stop and check out the situation there.
“While an ABS warning lamp doesn’t require a roadside fix, it’s important – given the other systems on the truck that work with ABS – to get it addressed by a technician as soon as possible.”
ABS Roadside Inspection: What to Expect
Because ABS activates only under specific conditions, it can be difficult for drivers to tell if the system is in good operating condition – that’s why the CVSA focuses its inspections on the yellow or amber malfunction indicator light (MIL). In-cab, they’re easily spotted on the dashboard – they are standard lights and look the same on all vehicles. Trailer ABS malfunction indicator lamps are located on the exterior near the red rear side marker lamp on the driver’s side; converter dollies also need to have the lamp located on the driver’s side. And they need to be clearly identified with the letters “ABS.”
“During a CVSA roadside inspection, the inspector’s going to first check to see whether ABS is required on your vehicle,” Hurley said. “If it is, they’ll ensure the lamps cycle on and off during the diagnostic check. If any of the lamps remain on, they’ll take that as a sign of a malfunction. Again: Not an out-of-service violation, but it is recordable, and you can be ticketed for it, so the best thing to do is address an illuminated lamp as soon as possible.”
Diagnostic Tools for Technicians
Brake manufacturers and OEMs provide diagnostic software designed specifically for the braking or vehicle systems they manufacture or include on their vehicles. The software is key to diagnosing and troubleshooting ABS faults on ABS systems since it provides specific information about what may be wrong with the system, as well as procedures on how to diagnose and repair it.
An example is Bendix® ACom® PRO™ Diagnostics Software, Bendix’s PC-based diagnostic tool that supports all of Bendix’s ECUs. For technicians not familiar with the tool, Bendix offers more than 20 training videos at the Bendix On-Line Brake School (www.brake-school.com), in-person three-day brake schools around the country, and the 1-800-AIR BRAKE line to get direct help on ACom PRO and brake system faults.
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