What Are Typical Mack Truck Regeneration Problems?

Mack regeneration problems often arise – and it can be a concern to operators when these happen.

Generally, a DPF regen, otherwise known as regeneration, occurs during the burning of accumulated soot in the DPF to prevent risks of clogging. Your truck may either carry out active or passive DPF regens.

Today, we will learn more about these regeneration problems and what can be done about them.

mack truck regeneration problems

Regeneration Problems And What The Causes Are

First, let’s talk about the two forms of regeneration. Passive regeneration happens when your truck is currently in motion, then the exhaust’s heat burns off the soot out of the DPF. As for the active regeneration, this occurs when the exhaust is not hot enough to eliminate the soot that has built up.

Thus, the engine lets out a bit of fuel right into the exhaust stream. This boosts the temperatures that help to burn the fuel and soot away.

Unfortunately, it may happen that the active and passive regens will fail. This is why the DPF filter may end up clogging. This will then cause the system to generate a forced type of DPF regen.

When you observe this happening, you need to pull over for safety purposes. This results in an unplanned downtime that can impact your schedule and productivity.

But at the same time, this is a necessary thing to do since you will end up causing damage to the engine and DPF if you fail to stop the engine. Your truck may also enter into a limp mode, which means bad news to your vehicle.

There are a few reasons why a DPF regen failure occurs. For instance, the hydrocarbon doser may malfunction. This injects a small amount of diesel into your truck’s exhaust during either a forced or active regens. As a result, the heat burns off any soot build up off your DPF filter.

When there is a clogged doser, this prevents an increase in the temperature that is required for a successful regen.

Additionally, there may be some concerns with your turbocharger. Your truck’s turbo pushes any compressed air to enter the combustion chamber. Then, this increases fuel efficiency and power of the internal combustion engine.

To initiate regeneration, the turbocharger must build sufficient heat that will trigger the entire process. But if your turbocharger is malfunctioning, this will prevent regens while causing a DPF failure.

Next, a clogged DPF can cause regen failures. As time passes by, the filters can have ash and soot build up that would require some professional cleaning. If the DPF has clogged up prematurely, it is unable to heat up to burn all the soot off during a regular regen process.

You can tell that the DPF filter is clogged by observing any frequent forced regens, as well as long ones that seem rather unusual. Typically, a forced regen lasts for less than 40 minutes. So, if your regen lasts more than that, this may mean that your DPF is clogged.

Another thing to take note of is a blockage in the DOC. The DOC or Diesel Oxidation Catalyst is the initial filter involved in the aftertreatment system. This component contains a metal catalyst responsible for oxidizing hydrocarbons, unburned particles of oil and fuel, and carbon monoxide in the truck’s exhaust stream.

When there is a blockage in the inlet face of your DOC because of too much carbon build up, this leads to a backpressure that restricts the flow of exhaust into your DPF.

Other Important Things To Consider

In addition to all of these issues, there are temperature sensor malfunctions that may occur. These sensors measure the amount of exhaust that go in and out of the filter. There is a sensor in the DOC and the SCR. If the sensor is not measuring the system well, then this can prevent a successful regen process.

It is also worth looking at the EGR fault codes that signal a problem. The exhaust gas recirculation system brings back some exhaust gas to the combustion cylinders of the engine. There are some relevant fault codes that may appear that can stop the DPF from regenerating.

With all these being said, a regen failure may occur and can signal a big problem. But if you are able to catch the issue as it is starting, then you can prevent serious and more expensive repairs in the future.

Read More: Are Volvo D12 Engine Problems Common?


Mack truck regeneration problems can occur due to a number of reasons such as the ones we have mentioned in this post. But by catching the problem early and finding the right solution, you can prevent the issue from snowballing further. A professional can help you address the problem and get your truck working properly in no time.



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