Let’s be honest, there are plenty of reasons why many fleets have developed such an unfavorable view of aftertreatment systems. Most tie back to three things: inconvenience, downtime, and cost.

“The need for forced regens and more frequent maintenance often frustrates drivers, inciting fleets to just disable the DPF (diesel particulate filter) regen function,” said Alex Parker, chief marketing officer and executive vice president of Redline Detection, a manufacturer of diagnostic leak detection equipment. “But disabling DPF regen often leads to a clogged filter, and that often leads to a costly derating of the truck.”

Technicians can also grow frustrated with aftertreatment systems. “Many fleet maintenance executives report a 9-times to 10-times increase in technician hours required to repair and maintain emissions systems since aftertreatment systems first came about in 2007,” Parker said.

Much of the aftertreatment system stigma ties back to those early years. According to Johan Agebrand, director of product marketing for Volvo Trucks North America, DPFs had a lot of metal stresses and potential cracking due to the extreme thermal expansions and contractions created from temperature differences. Additionally, for selective catalytic reduction (SCR) and urea dosing systems, there were problems with crystallization and an inability to build up heat in all duty cycles.

“I often remind myself that the diesel engine has had 140 years to mature,” added Len Copeland, product marketing manager for Detroit Products, a manufacturer of diesel engines, e-powertrains, transmissions, axles, safety systems, and connected vehicle services. “Aftertreatment systems have only been around a tenth of the time and have already evolved rapidly. That said, the very first aftertreatment systems were not without some learning opportunities.”

In early systems, Copeland says the top three issues for many fleets were DEF (diesel exhaust fluid) dosing systems, DPF cleaning processes, and thermal management.

“Early aftertreatment systems often dosed DEF pneumatically,” Copeland said. “That provided excellent atomization, but a dirty air system could lead to major issues. As such, most manufacturers appear to have gone to an electromechanical system that is able to achieve almost the same atomization with significantly reduced issues.”

For thermal management, Copeland points to physical improvements such as exhaust insulation between the turbo outlet and aftertreatment systems inlet. There have also been software improvements such as Detroit’s Auto-Elevate and Asymmetric Injection which help maintain aftertreatment system temperatures for more successful passive regens.

The most recent version of Detroit’s aftertreatment system was released this year to meet GHG (greenhouse gas) Phase 2 regulations. “With this update, we are able to extend DPF replacement intervals up to 640,000 miles or more while further improving the SCR to increase efficiency at lower temperatures,” Copeland said. “The DOC (diesel oxidation catalyst) has also been improved to allow for lower minimum temperatures during dosing. These improvements help the system clean exhaust better at lower RPMs.”

Volvo’s Agebrand points to other recent aftertreatment system improvements. “Some major changes include the fact that the SCR catalyst actually does a catalytic conversion in an increased temperature range. Thus, more variety in load and temperature from the engine will still result in a catalytic reduction of NOx emissions,” Agebrand explained.

Dosing systems have also improved in both algorithms and hardware. “This enables the systems to operate in a variety of conditions and with higher efficiency,” Agebrand said. “Material production design has also facilitated more compact systems that are easier to service without reducing efficiency.”

The need for specialized training and tools

Despite 14 years of aftertreatment system improvements, some fleets still have a bad taste in their mouths.

“When 2007 emissions standards were released, there was little to no training for the fleet technicians on how to diagnose, service, and maintain the aftertreatment systems,” said Randy Griffith, director of technical sales at Emission & Cooling Solutions (E+CS), a family-owned company with nine shops nationwide. According to Griffith, this general lack of OE training is still the case in 2021. That is why E+CS specializes in helping technicians understand basic functions and diagnostic procedures for aftertreatment systems.

“We have also found that many parts are replaced when there is no need to replace based on age or hours,” Griffith added. For example, a DOC should last many years, but a technician is often told to simply change it rather than find the root cause. “Customers get frustrated and decide to delete,” Griffith said.

Even for those fleets that have attained the proper training, more hurdles exist. One is the need for specialized equipment.

“The cost of tools and equipment needed to diagnose and service these systems is a newer problem for fleets,” Griffith said. “Smaller fleets are particularly affected because they previously could get by without having modern scan tools and equipment.”

Another challenge is simply the cost of exhaust items. While exhaust used to be a minimal expense for a fleet, Griffith says it has risen to the top of the list behind fuel, oil, and tires.

“Aftertreatment components are expensive,” Griffith said. “Without knowledge of the system and the proper diagnostic equipment, a fleet can easily spend tens of thousands of dollars to fix one system. Furthermore, fleets will typically deal with an ongoing occurrence until the root cause is repaired correctly.”

How some fleets illegally bypass aftertreatment systems

Given all of these hurdles, some smaller fleets have gone the way of deleting (removing) entire systems from a truck. This creates both environmental and legal issues. Additionally, Griffith says there can also be some drivability issues that cannot be repaired through the typical OE dealer channel.

“From my understanding, an OE dealership will not touch a truck in which the aftertreatment systems have been tampered with,” Griffith pointed out. “This leaves fleets with very little support if there is a major issue down the road.”

Nonetheless, some fleets make the ill-advised decision to tamper.

Griffith stresses the fact that E+CS has never engaged in the removal or bypassing of an aftertreatment system. “We are in the business of cleaning and repairing aftertreatment systems as well as providing aftermarket products to keep systems intact as they were intended to be,” Griffith emphasized. That said, his many years in the industry have exposed Griffith to a story or two. Plus, his knowledge of engines and aftertreatment systems allows him to see where tampering could take place.

“I was in a shop in early April where a customer brought in a truck with a head gasket issue,” Griffith related. “When the technician went to clean the filters, he found that the DPF had been drilled out due to contamination. According to the owner/operator of the truck, he had no idea the truck had been deleted when he’d recently purchased it.”

Drilling out the DPF is a common way people delete their aftertreatment systems. This is generally done with a hole saw to make large passages through the filter media so it can bypass the filtration. Generally, this will cause aftertreatment codes which will then need to be either left in the system or programed out of the system.

Another bypass method Griffith has heard about is the installation of block-off plates in place of the EGR cooler. That keeps the system from recirculating the exhaust back into the engine. “This is common on early aftertreatment systems,” Griffith added.

Tampering is illegal and costly

Just like E+CS, Volvo does not condone any activities that seek to bypass or delete an aftertreatment system. “It is considered active tampering with an emissions system and is against the law,” Agebrand stated.

As Agebrand pointed out, the environmental consequences of tampering are also quite clear. “NOx emissions and particulates would not be controlled from the vehicle, and the air we breathe would not be as clean,” Agebrand said. “When it comes to a person or company actually tampering with a vehicle, there are many consequences including voiding of the warranty, hefty fines from the EPA (Environmental Protection Agency) or CARB (California Air Resources Board), and possible imprisonment.”

Some OEs have taken steps to guard against active tampering. For instance, Agebrand says Volvo has developed several functions and algorithms in combination with hardware sensors to detect any such tampering or systems that are not working. “If any customer tries to bypass the system, for example, the truck‘s check engine light will activate, and the vehicle will go into a ‘limp home’ state with low speed, ultimately stopping if this is not addressed by a service technician,” Agebrand explained.

Detroit Products’ Copeland said it’s important to ask why someone would want to bypass or remove an aftertreatment system in the first place. Typical answers are a perceived reduction in performance or the desire to reduce maintenance costs and downtime. However, perception is not reality.

“The aftertreatment device acts as an excellent muffler, especially when paired with a quieter down-sped engine,” Copeland explained. “That often leads to the perception of low power, even though power is tested by the EPA since most emissions regulations are measured in g-hp/hr. This means a DD15 engine with 505 horsepower is truly producing 505 horsepower, for example.”

With respect to maintenance costs and downtime, Copeland said parked regens and unexpected repair costs should be minimal when proper use and maintenance of a newer aftertreatment system are adhered to.

“Those costs are also likely to be offset by the extended service intervals of modern equipment,” Copeland added. “Some engine oil changes are 75,000 miles and DPF intervals extend past 600,000 miles.”

The bottom line is that the cost of deleting an aftertreatment system is often much more than the cost of proper preventive maintenance for the life of the truck.

“A standard PM is under $1,000, but a new ECM (electronic control module) to work with a deleted truck can be $4,000,” E+CS’s Griffith explains.

Innovative solutions improve aftertreatment maintenance

Even with adequate training, service tools, and preventive maintenance measures, most fleets could still benefit from additional aftertreatment system assistance. Fortunately, there are many aftermarket solutions that can help.

“Here at E+CS, we have a process known as the DPFRENU process,” Griffith said. “This process is used to service the DPF filters themselves and can increase the longevity of an aftertreatment service. DPFRENU can also reduce strain on the engine by decreasing backpressure and creating more soot-loading capacity.”

As Griffith explained, good DPF cleaning programs that focus on flow rate and capacity can help dramatically decrease the cost and downtime associated with aftertreatment issues. Since there are many different processes and types of equipment available, Griffith said it is important for a fleet to partner with a good service provider. That company can proactively maintain the fleet’s aftertreatment systems, as opposed to reactively deleting or removing systems that are not functioning properly.

Detroit’s Copeland said fleets should simply refer to Detroit’s guidelines on sourcing a remanufactured filter rather than having it cleaned by a third party.

“Our remanufacturing process features an extensive, proprietary, environmentally friendly washing service for DPFs,” Copeland explained. “This cleaning process removes more than 95 percent of the ash residue from the DPF. Incorrectly removing the harmful ash residue in the filter can create hot spots. That can lead to a cracked DPF, downtime, and additional maintenance costs. Our process is far more effective than using a ‘bake and blow’ method.”

Getting to the root of upstream air leaks

Redline Detection’s Parker said certain product innovations can also help diesel technicians proactively seek out air leaks, which happen to be the root cause of many DPF-related issues.

Research from Redline Detection suggests that an “upstream component fault” is the most common cause (89 percent) of DPF failure. This can be caused by small air leaks that are often undetectable. These upstream leaks create an inconsistent air/fuel ratio that can lead to downstream aftertreatment faults and, ultimately, DPF/SCR failure.

According to analysis from Redline Detection, the most problematic upstream component failures are:

• Leaking injectors
• Leaking exhaust pipes
• Manifold gaskets
• Coolant leaks
• EGR cooler leaks
• Doser valve (aka 7th injector)
• Turbo failure or housing failure
• Sensors and wiring harness failure

The challenge for fleets is identifying when and where these seemingly undetectable upstream air leaks exist before they result in a failed aftertreatment system. As Parker pointed out, the old-school method isn’t effective.

“Standard practice has always been to pressurize a system by starting the engine, slide under the running truck, spray soapy water, and look for bubbles,” Parker said. “That method is not only dangerous, but also makes it nearly impossible to reach many of the key components in a modern truck. Another problem with the soapy-water method is that many modern trucks’ computer systems will not allow the engine to produce boost while sitting in a bay.”

An alternative to the soapy-water method is to use an ultrasonic listening device. But in a noisy shop, that can prove to be impractical, as well.

So, what is a heavy duty technician to do?

The Technology & Maintenance Council (TMC) has developed a Recommended Practice (RP 375) that utilizes high-pressure leak detection technology to address upstream leak detection in aftertreatment systems.

Redline Detection’s HD PowerSmoke technology uses regular compressed air to maintain a variable pressure of 2 to 20 psi throughout the intake and exhaust system. Compressed air is injected into the system, followed by a visual vapor that replicates the boost load of a running engine. The vapor flows through the truck’s hoses, tubes, and related components. If there is a leak, the vapor escapes at that precise point, allowing the technician to visually identify the location.

An added bonus to this procedure is the fact that the engine can remain safely off. As importantly, the procedure is quick and easy.

“It typically takes less than five minutes to test an entire aftertreatment system,” said Mark Hawkins, head of technical products at Redline Detection. “The technician seals the largest orifices on the engine and the exhaust with our intake adapters. Then the visual vapor is introduced within those two points. It’s designed so that when it inflates, it creates the perfect seal regardless of make or model.”

Parker says Redline’s unique leak detection technology can be used for triage diagnostics when a truck comes into the bay with an issue. Additionally, technicians can use this RP 375 procedure for preventive maintenance in an effort to locate faults before they trigger excessive forced regens or derate.

As a preventive measure, Hawkins says some fleets conduct a visual vapor leak inspection every 90 days. Regularly inspecting for leaks can help prevent costly system failures. “A lot of leaks are found prior to an engine light coming on,” Hawkins pointed out.

Fleets have plenty of solutions at their disposal to help get a better handle on aftertreatment system management. From training and tools to innovative services and procedures, it is up to fleets to take advantage. Yes, some investment is necessary. But when potential costs and other downsides of poor aftertreatment system maintenance are factored in, the ROI picture becomes a lot clearer. Then, when you look at the potential costs and downsides of tampering with an aftertreatment system, the ROI really comes into focus.