What Is Regen On Diesel Trucks?

When soot builds up inside the diesel particulate filter (DPF) to the extent where the vehicle is no longer functional, a forced regen occurs. When this happens, the vehicle must pull over and begin a self-cleaning process that can take up to 40 minutes — time that could have been spent driving.

How often should a diesel truck Regen?

The visible exhaust is soot, which is the black smoke you see coming from the stacks. It consists of unburned fuel, carbon, and other solid matter.

The Environmental Protection Agency (EPA) began enforcing new pollution standards for all diesel engines in January 2007. Diesel emissions are considerably reduced as a result of these stringent standards. In fact, between 1990 and 2007, the EPA cut the permitted NOx levels in diesel exhaust by a total of 80%.

The EPA has now lowered permitted particle matter in diesel exhaust by 90 percent as a result of the 2007 restrictions. And the difference isn’t just visible on the roadways; it also manifests itself in significantly cleaner air and a healthier ecosystem.

To meet the EPA’s particle matter standards in 2007, all manufacturers used an Exhaust After-Treatment System. Every diesel truck sold in the United States and Canada since 2007 has been equipped with an exhaust aftertreatment system (ATS).


The Diesel Particulate Filter is the technology used in this After-Treatment System. The DPF is also referred to simply as the DPF. The DPF takes the place of the previous muffler and traps.

Rather than releasing soot into the atmosphere, the DPF collects it and then oxidizes it with heat. As a result, the air that exits the exhaust is substantially cleaner. Soot is regenerated into clean carbon dioxide gas and water vapor on a regular basis. The end result is a clean xhaust with no odor or fuel smell. This cleaner exhaust will not blacken your trailer or the inside of your exhaust stack!

The DPF is a ceramic filter with thousands of microscopic channels. The DPF gathers the soot (particulate matter) that is produced by the engine.

Soot is caught along the channel walls when the exhaust passes through these channels, preventing it from exhausting through the stacks and protecting the environment. Solid substance has become entrapped…

The DPF must clear the soot that has built up along the channel walls on a regular basis. This is referred to as “regeneration.” It’s like a – a self-cleaning oven, if you will.

Regeneration is an oxidation process that removes soot from a filter by heating it. The process of regeneration is actually rather easy. There are just two stages in the process: passive and active.


When the engine reaches the required operating temperature during constant drive, passive regeneration occurs naturally. An oxidation catalyst coated with precious metals is found in the DPF. Passive regeneration occurs when the catalyst in the DPF heats up enough to oxidize the soot and convert it to C-O-two during typical highway driving. The exhaust stack is where the C-O-two leaves. Any residues that are left behind are transformed to harmless ash and collected in the DPF canister.

The process is continuous, thus the DPF will start passive regeneration as soon as the vehicle achieves operational temperature. This implies you won’t notice any differences in how the car runs because you won’t have to do anything to make passive regeneration happen. Passive regeneration is going all the time, and you’re not even aware of it!


Passive regeneration is insufficient to avoid soot buildup in the DPF over time. That’s when the second cleaning stage kicks in. “Active regeneration” is the term for this. When your engine’s computer detects that the DPF requires cleaning and the operating temperature is high enough, an active regeneration is initiated. Typically, the system will commence active regeneration on its own. It’s possible that you’re not aware that a regen is in progress.

When a little amount of fuel is put into the exhaust stream between the turbocharger and the DPF, active regeneration begins. This fuel is atomized into a very fine, non-burning spray. Instead, it generates extreme heat – up to 1100 degrees Fahrenheit – when it makes contact with the catalyst on the DPF, oxidizing any leftover soot on the ceramic filter. C-O-two leaves the stacks, collecting ash in the canister.


Active regeneration might happen as frequently as once a day, depending on your driving habits. It can happen even more frequently if you do a lot of stop-and-go driving. The frequency is determined by the duty cycle and the amount of soot collected – it may be once a day or every other day. Active regeneration can take up to a half-hour or longer.

After an active regeneration has begun, if you slow down or stop the car, the regeneration may be interrupted, and you may have to restart it. So, if the dash shows that another regeneration is underway, don’t be alarmed.

The DPF will need to be cleaned by a specialist on a regular basis to remove the ash that has accumulated in the canister. This can be accomplished in as little as 30 minutes.


Fuel is injected during active regeneration, which can elevate temperatures in the exhaust stream and aid regeneration. This could take 20-60 minutes and use up to 1/2 gallon of gasoline. It’s usual to hear a tiny whistling.


Only when moving can the vehicle regenerate on its own. The regen will come to a halt if the driver slows or stops the truck. A parked regen must be initiated by the driver or a technician if a regen is required when the vehicle is stopped.


In most cases, nothing. During the regeneration, the vehicle must be kept at working temperature, therefore highway driving is recommended. Simply drive as you would ordinarily.

The exhaust outlet temperature is particularly high during active regeneration. So keep an eye on your surroundings if regeneration is about to commence. If you’re approaching a location where high exhaust temperatures could be dangerous – such as a crowded construction site, a gas station, or a tunnel – you should turn off the regen.

To disable regeneration, press enter on the DID control stalk until you’re back on the highway and can enable it again. Alternatively, wait until you’ve come to a safe stop and may do a “parked” or “manual” regeneration.

When the vehicle is stopped or driving at less than 5 miles per hour, the High Exhaust System Temperature indicator glows during active regeneration. This is to remind you to be cautious of your surroundings when the vehicle is stopped or moving slowly during an active regeneration.

The Request Regeneration Icon will remain illuminated if an automatic regeneration is interrupted, and the message “Manual REGEN Required” will appear on the Driver Information Display.


If the vehicle slows down below 5 mph after running on the highway and building heat in the DPF, a warning yellow lamp may illuminate. “HIGH EXHAUST TEMPERATURE” implies “HIGH EXHAUST TEMPERATURE.” This does not imply that something is wrong. When the temperature returns to normal or if the vehicle speed exceeds 10 mph, the lamp will switch off.


If the truck will be in an area where high exhaust system temperature is an issue, you may want to disable regeneration (parking indoors to unload).

You can cancel regeneration if it is already in progress and you find yourself in a dangerous situation.

Use the Driver Information Display menu and the right-hand stalk controls to disable regeneration.

1. Scroll to Aftertreatment using the controls.

2. Hit the ENTER key.

3. Press ENTER after scrolling to Cancel REGEN.

4. Select Disable REGEN from the drop-down menu.

KEY IN ENTER. The box labeled Disable REGEN will be checked.

Scroll down to the after-treatment menu using the Driver Information Display menu and the right-hand stalk controls. “Cancel REGEN” is the first option, followed by “Disable REGEN.” This will stop the regeneration process until you ENABLE it again.

When regeneration is deactivated, the letters ATS will be displayed in the Information display with an X through them. This indicates you’re stopping regeneration from taking place, and if this continues long enough, the car will shut down.

Return to the after-treatment menu, select CANCEL REGEN, and then ENABLE REGENERATION as soon as possible to enable regeneration.

The ATS symbol with the line across it will disappear from your display once you click the X in the enable regeneration box.

What does Regen mean on a diesel engine?

The goal of regeneration is to remove particulate matter, or unburned fuel (also known as soot), from diesel engine exhaust. It’s a typical and required aspect of complying with EPA-mandated Tier 4 rules by lowering harmful emissions.

What happens if you don’t Regen a truck?

The process of regenerating, or regenerating, the DPF filter is the process of burning the soot deposit inside the filter. If you can’t start a regen, you’ll get trapped in a derate, which will eventually cause the engine to shut down.

When should I Regen my truck?

When the truck requests a parked DPF regen, this indicator will illuminate. This feature is designed to display when the soot level in the DPF filter reaches a specified level, allowing the truck to continue working.

When your truck requests a parked DPF regen, it signifies the passive DPF regen your truck has already completed was insufficient to burn the soot in your DPF filter.

Yes, to put it succinctly. If you continue to drive your truck without performing a parked DPF regen, it will enter derated mode.

When the truck automatically does a DPF regen, it is known as active DPF regen. When the soot level reaches a specific level, the active process to burn the soot off begins. When your engine is in “active mode,” you may find that it runs faster.

There are numerous reasons for a failed “active regen,” as it is dependent on certain criteria being satisfied in order for it to occur.

If you fail a parked DPF regen, you should be warned that continuing to drive will just result in more problems and/or derates. As a result, be aware of what’s going on so that you can get help as soon as feasible.

It will keep regenerating until the soot level reaches ‘low’ or ‘zero percent.’ On the dashboard of some trucks, you can see your soot level gauge.

DPF regen while parked: The truck requests DPF regen, which you initiate by pressing a button on the dash.

Forced DPF Regen: At the dealer level, a diagnostic scan tool will begin a forced DPF regen. The conditions do not have to be ideal, and they will cause a regeneration to occur.

The system undergoes a forced DPF regen to ensure that the aftertreatment system is in good functioning order. The truck is ready to travel if you can execute a forced DPF regen without any fault codes or difficulties emerging.

For example, a 2013 Volvo D13 has SPN 4094 FMI 1, MID 128 PSID 90 FMI 14, and SPN 4094 FMI 1. The dashboard comes to life (DEF Quality being evaluated, 5mph temporary removed, continue driving).

The only way to clear this error code is to ensure that your DPF/SCR system is free of additional issues. This fault will remain active until a service forced DPF regen is performed and the ECM/ACM runs through all of the checks to ensure that the NOx sensor levels are within the required limits, at which point the fault code will become inactive.

So, even if you have DEF quality fault codes, you can start a forced DPF regen. To clear the issues, the truck must run through all of its checks to ensure that the system is within the manufacturer’s restrictions. Volvo, Mack, Detroit Diesel, and other manufacturers employ this technology as well.

A forced DPF regen will ensure that any soot buildup in the DPF / SCR System is removed. If you remember to perform this more than once, your DPF system may last longer. Once a month, we recommend doing a service DPF regeneration. You may get greater MPG since your filters have been cleaned and your exhaust system is circulating air more efficiently.

OTR Performance includes a mechanism that allows you to initiate a forced regeneration. This can be done in 30 seconds to 4 minutes using the OTR reset tool. We also have an app called OTR Diagnostics that allows you to run advanced diagnostic commands from your mobile device or tablet, such as a forced DPF regen. You can also read and reset fault codes, monitor live data, and do a lot more with OTR diagnostics. Take a look at it here.

  • If the regen begins and then stops, you may have a problem that prevents the regen from occurring. Check for errors and give it another shot.

Can you regen a truck while driving?

One of the most subtle threats to the health of your truck’s engine is soot buildup. Regens must be conducted on a regular basis to keep your truck operating and safe to operate. However, needing to pull over and conduct parked regens takes time away from time spent on the road. You might be wondering if you need to park completely and wait for the soot to clear from your engine. Is it possible to regenerate while on the road? So, we did some investigation and discovered the answer for you.

While your truck is running, it can and typically will go through the regen process properly. During steady driving, your diesel particulate filter, or DPF, conducts routine passive regen as needed. Active regeneration occurs as well, with the optimum results occurring at motorway speeds. However, there are times when a totally parked regen is required, most commonly after prior regens have been interrupted.

As you can see, many types of regen occur at various stages of the DPF’s fuel oxidation process. The tough part about these distinct types of regen is that they require different driving techniques from your vehicle. Continue reading to learn more about what you and your truck must do to comply with regens.

Does DPF regeneration cause smoke?

During DPF regeneration in a Diesel engine with a Diesel particulate filter (DPF), high-sulfur fuel produces white smoke comprising odorous and hazardous pollutants. The SO3 was then desorbed and turned into white smoke.

Can you turn off engine during regen?

Active regeneration is a risk-free option, but it is not without dangers. If you merely make short drives about town in your automobile, it’s easy to disrupt the process. If you turn off your automobile while it’s in the middle of active regeneration, it could cause problems because the filter hasn’t been properly cleansed.

How does a regen work?

Emissions equipment for diesel trucks has evolved significantly over the years. EGRs, or exhaust gas recirculation systems, were required on all heavy-duty diesel pickups in 2004.5. Essentially, it converts exhaust into inert gas and reintroduces it into the combustion process. The EPA then mandated the use of a DPF in pickup trucks in 2007.5. The DPF (Diesel Particulate Filter) is an exhaust filter that collects soot and unburned fuel. When soot accumulates, the exhaust warms up to burn the soot away. Diesel Exhaust Fluid has been utilized to treat NOx emissions since 2011, in addition to EGR and DPF for carbon emissions.

The DPF is an important component of treating diesel emissions, and each OEM uses and runs their DPF in a unique way. The DPF in the LML Duramax from 2011 to 2016 is detailed below.

How long does Duramax Regen last?

lights turned on, and it was as if they were ticking away like a clock. After 45 minutes, the idle returns to its regular burble. You climb out of your pickup and inhale the wonderful scent of achievement (or burnt soot if this is going as glorious as we imagine). This would be the typical experience for most other operators who use our product for preventative maintenance. Unfortunately, all too often, things do not go as planned.