Bendix Tech Tips: Troubleshooting, Diagnosing Security Systems


A dashboard warning light can send a simple, clear message: something on your truck needs to be checked. But on today’s complex vehicles, and particularly with regard to their increasingly interconnected safety systems, knowing exactly how and what to check can mean the difference between hours and days of costly downtime.

This article in the Bendix Tech Tips series provides tips on troubleshooting and diagnosing advanced safety technologies, from the fundamentals of anti-lock braking to components that enable collision mitigation and more.

just start

“Sometimes the first response to an indicated electronic problem in crash mitigation systems may be to start removing and replacing components,” says TJ Thomas, Bendix’s director of marketing and customer solutions – controls. “But often times one component is not the problem, so we recommend that you start by running a diagnostic software tool that displays a system view of what is on the vehicle, including key vehicle components. ”

This assessment can give the technician a quick overview of what is going on, especially when multiple components have similar active DTCs, such as J1939 communication errors.

The technician may also look for frayed wires, corroded connectors, or blown fuses. Additionally, equipment such as cameras and speed cameras should be checked to ensure that they are not obstructed by elements such as road debris, snow and ice.

Also, some DTCs are “self-cleaning,” says Thomas. “This means that by simply correcting the situation – by removing the obstructing debris, for example – the warning lights and associated error codes will be disabled.”

Service data sheets should list these types of DTCs so the technician can know what types of conditions are causing them, Bendix says.

If that initial approach turns out to be empty and it looks like the problem is something a little deeper, then having the right tools and the know-how to use them is key to getting trucks back on the road and in good working order as quickly as possible. possible.

Everything is connected

More than ever, the various systems in a commercial vehicle are intertwined, with multiple Electronic Control Units (ECUs) sharing necessary information over the J1939 network. For example, automated transmissions depend on engine input to operate properly and at their highest efficiency.

“Apparently everything on these trucks communicates with everything else,” says Brian Screeton, Bendix Supervisor – Technical Service Training. “So the best advice we can give for diagnosing faults in higher-level safety systems like adaptive cruise control is to make sure you look at the whole truck first.

“If a driver reports an adaptive cruise fault, a technician can hook up their diagnostic tool just to the radar, and there may not be an active fault, but it ends up going down a rabbit hole and spending time trying to fix idle faults, when it turns out there’s an engine problem causing the whole thing. Faults in a system can be caused by a completely separate system component,” explains Screeton.

A J1939 fault, for example, will affect multiple systems, so a technician should first investigate this fault and then run the diagnostic tool again to see if the individual faults in the system are resolved. Because of this possibility, Screeton points out that before making any changes to a vehicle, technicians should run a full Diagnostic Trouble Code (DTC) Report as a reference, to know the full condition of the vehicle before starting work. .

The right tools

Before assuming that an active DTC from an advanced security system means something is wrong with that system, technicians should ensure that they are using a tool that gives them visibility into all active DTCs being broadcast on the vehicle’s J1939 network. Bendix ACom PRO is one such tool, but the important thing is to have a diagnostic tool that displays full vehicle DTCs.

“A tool that shows you an active DTC on the engine retarder, for example, tells you that you need to fix that problem first because it may be the cause of your adaptive cruise control DTC,” says Screeton. “We recommend that technicians always troubleshoot active engine faults first because of how they affect other system faults.”

When connected to a vehicle, the ACom PRO software automatically detects and gathers active and inactive DTCs from all Bendix electronic control units in the vehicle, as well as key vehicle ECUs, such as engine and transmission. This roll call shows what is on the vehicle, eliminating the need for a technician to guess from a pre-populated list of components.

ADAS addressing

Advanced Driver Assistance Systems (ADAS) that provide features such as Adaptive Cruise Control and Automatic Emergency Braking are deeply integrated through their communications with systems such as the brakes, engine and transmission . They also include their own ECUs and sensors such as camera and radar units – components that require an extra degree of caution.

“The physical components of the stability and crash mitigation systems generally only require maintenance if modifications have been made to certain parts of a vehicle. If you are performing a front end alignment or working on the steering linkage, for example, you will need to recalibrate the steering angle sensor according to the manufacturer’s guidelines,” Thomas said. “Before a technician adjusts a camera or radar, we insist that they address faults first J1939 or engine faults. You don’t want to waste time replacing or realigning a sensor if it’s not needed.

Additionally, modern diagnostic tools increasingly have the ability to make changes to systems, from calibration to reconfiguration. Bendix strongly recommends that any individual technician confirm with maintenance or fleet management before making any performance changes to ensure the outcome will be as the fleet wants.

Stay up to date

“Another thing we get feedback on from fleets is the value of continuing education,” Screeton says. “We have our Brake School sessions where we explain how these systems work and how our diagnostic tools work, plus we provide know-how. This really shows the importance of regularly checking in with manufacturers and suppliers for the latest product information and maintenance methods. »

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