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Tips for Minimizing Aftertreatment Failures in Commercial Trucks

December 1st 2019




Tips for Minimizing Aftertreatment Failures in Commercial Trucks,

Greg Munden is the owner of Munden Ventures Ltd., a 4th generation log harvesting, trucking and commercial vehicle maintenance operation based in Kamloops, British Columbia. As a Past Chairman of the British Columbia Trucking Association (BCTA) and current Secretary/Treasurer of the Canadian Trucking Alliance (CTA),Greg spends a good deal of his time working on industry issues.

In the modern trucking industry, the issues associated with the downtime caused by engine after-treatment emission systems are rather familiar. From 2007 onward, these systems have represented the single most troublesome system in keeping commercial trucks on the road. And it is not an OEM-particular issue – whether you run Kenworth, Peterbilt, International, Freightliner, Western Star, Mack, Sterling or any other, the issues with after-treatment are common amongst them all.  

Today’s aftertreatment systems include such terms as SCR (selective catalyst reduction – most commonly used term for today’s emission reduction systems),DOC (diesel oxidation catalyst),DPF (diesel particulate filter) and DEF (diesel exhaust fluid). While the technology is complicated, the steps for using these systems from a trucking business standpoint don’t need to be; these steps are, however, extremely important.

It is hard to find a trucking company that hasn’t struggled with the seemingly incessant fault codes delivered from the systems – which often result in quick derates in power and strand trucks and their professional drivers in rural locations without access to the technology (let alone parts) to get them up and running. That said, the systems are improving as sensor tolerances have been widened and OEM’s have worked to upgrade the entirely unacceptable performance of early generation systems.

Here is a list of common after-treatment issues as well as the simple steps you can take to minimize the likelihood of having the issues to begin with.

Whether you are talking about the diesel exhaust fluid (DEF) delivery system or the DPF system, both can present with some common issues.

1.    Contaminated DEF Fluid –The DEF delivery system is a highly sensitive system that does not handle contamination well. Although it seems intuitive to ensure your DEF fluid is kept clean, this is sometimes easier said than done. DEF tanks are commonly mounted off of the frame on the truck and, as a result, are susceptible to all of the elements in the environment from rain, snow, ice, mud, etc. Tanks in areas of inclement weather or vocational applications can commonly be covered in dirt at the time of adding DEF. Cleaning the area around the fill bung before removing the DEF tank cap can help minimize the chance at debris falling into the tank.

 System Diagram

While fueling at Cardlock sites that offer bulk DEF fueling can help to minimize the chance of contamination, many areas don’t have this service available and drivers are required to either pack jugs of DEF with them or purchase jugs from local stores having DEF sales. Depending on where the jugs are stored in-transit, they can also be susceptible to environmental contamination. As well, in an effort to save money on over-the-counter DEF costs, companies will sometimes have drivers re-use jugs and fill them at Cardlock locations that have bulk DEF available or at company terminals with their own bulk DEF stations. Unfortunately, re-used containers have the increased likelihood of contamination over time, both the outside of the container and internally.

Whenever possible it is recommended to purchase DEF at Cardlocks or use new containers only to minimize the chance of contamination.

Contaminated DEF is not easy to see with the naked eye, and the distinction between “clean” and “contaminated” DEF is a topic that often leads to disagreements between truck owners and OEM dealers. In most cases, “contaminated” DEF is an easy out for the engine manufacturers in warranty denial. Often, “contaminated” DEF is often pointed to as the cause for DEF dosing pump failures, discussed below.

2.    DEF Storage - A contributing factor to DEF contamination can arise from how it's stored. Keep DEF in a temperature-controlled environment out of sunlight and freezing conditions whenever possible. Both of these conditions can cause DEF to crystallize These DEF crystals are another element of contamination that can plug the dosing pump and deny a warranty claim, not to mention strand your truck after throwing an aftertreatment code. 

3.    Preventative Maintenance of DEF Filtering –Most current DEF systems include at least 2 levels of filtering. The first is a typical filter that you might expect in a fuel or oil system, while the second is a sock filter that offers another level of filtering before the DEF dosing pump. Proactively changing these filters on either 6-month or 12-month intervals, depending on your operating environment and likelihood of introducing contamination, can be a valuable and cost-effective way of reducing one of the most common system failures – the dosing pump.

The dosing pump deliveries DEF from the DEF tank to the SCR system for the burning of exhaust. This dosing pump can handle very low levels of contamination before failing. Failure of a dosing pump due to contamination is almost never a warrantable failure, even with near-new trucks, and can lead to very large bills once dealers drain and clean DEF tanks, change out the dosing pump, and refill the tank with fresh (OEM priced) DEF.

When encountering DEF-related fault codes, some fleets have gone so far as to drain DEF, clean the tank, refill with fresh DEF, and then deliver the truck to their OEM hoping for a warrantable repair and to minimize the arguments that inevitably occur over “contaminated” DEF. At a minimum, we recommend shining a light into the DEF tank to attempt to view the contamination level of your DEF fluid. Any sign of debris floating in the DEF should be a warning to the truck owner that a warrantable OEM repair is at risk.

4.    Heated DEF Lines –Another common point of failure (albeit increasingly less common as an issue in very current DEF systems),heated DEF lines in earlier DEF systems were likely failure points. Unfortunately, aside from ensuring these lines are tied up and not at risk for getting ripped off in off-highway environments, there isn’t a lot that fleets can do to avoid DEF line failures. Just know that heated DEF lines are often very specific to each OEM application and may not be readily available. Diagnose quickly and get your order in to minimize downtime.

5.    DPF filter –This filter is housed within the DPF housing and is the unit that ultimately collects the contamination left behind after exhaust burning. Over time, like any filter, the DPF filter plugs up and eventually requires cleaning. This cleaning is accomplished by a combination of pneumatic cleaning (stage 1),“baking” the residue left in the filter in ovens custom-built for this job (stage 2) combined with pneumatic cleaning, or wet-washing (stage 3),plus the thermal (baking, stage 2) and the pneumatic (stage 1) steps.

The longer a fleet waits to clean filters (at some point fault codes and engine de-rates won’t let you wait any longer),the less likely they are to be cleaned with the best result. Multiple cleanings of the same filter will eventually be unsuccessful, and the filter will need to be replaced at a very significant cost. The best preventative work to do is clean filters prior to them becoming so clogged that they prompt an engine derate that forces you to.

6.    Wiring and Connections –If you have spent any time in this industry, it is no surprise to hear that wiring and connections not only continue to plague after-treatment systems but are also one of the most likely sources of issues across a commercial truck or trailer. Whether due to chemicals applied to the roads to manage snow and ice, the ever-increasing use of electrical wiring to control more and more complex truck systems, or lower quality wiring and harnesses being used by OEM’s, there are multiple factors leading to the ongoing issues with maintaining truck electrical systems.

Aside from ensuring wiring is tied up and protected from rubbing, the most important prevention is to ensure connections are tight and the chance of introducing moisture is minimized. Cautioning drivers or terminal wash crews to avoid directing a lot of water at the after-treatment harnesses is generally all that can be done to minimize electrical issues.

Multiple electrical-related fault codes all occurring suddenly with the after-treatment system is a good hint for fleet technicians to begin troubleshooting by looking at electrical harnesses for continuity, corrosion and/or pin damage.

7.    Engine Re-Gens and Operating Temperatures – Of course, engines and aftertreatment systems are supposed to automatically handle re-gens (or burns) to clean out DPF filters.  Another preventative steps fleets or truck owners can take is to periodically force a “manual” regen. In most cases, access to technician software is needed to make this happen and so is restricted to shops with that technology. Taking the often 30-40 minutes to allow a manual regen to complete a cycle and create the extremely high heat needed to clean the DPF filter is a good way to minimize sooting and the resulting fault codes that can follow.

 aftertreatment unit

Example of a single-module aftertreatment unit (DPF and SCR in one)

While it is not likely to expect any amount of preventative maintenance to eliminate aftertreatment issues, a little maintenance can go a long way to reducing the frequency of these issues as well as the cost when they do occur.

Munden Ventures can help you with your aftertreatment and other truck and trailer repair and maintenance needs, including emergency roadside service. We have expert technicians and software to assist with diagnosis and repair of aftertreatment fault codes and issues, often at a fraction of the cost you might experience at an OEM. As well, we can help you to avoid some of these issues with the implementation of a Preventative Maintenance program. Visit our repair services today at www.mundentrucking.ca/parts-and-service or contact us at www.mundentrucking.ca/contact.