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DPF Regeneration: Passive, Active & Manual Regeneration


DPF Regeneration: Passive, Active & Manual Regeneration


What is a DPF?

How long should a DPF last?

What is DPF regeneration?

What are the types of DPF Regeneration?

How to Regenerate a DPF manually


What is a DPF?

DPF stands for ‘Diesel Particulate Filter’ and this plays an important role in diesel engines. DPF’s are designed to trap and store particulate matter (soot) that is produced by the diesel engine during normal driving. The DPF allows exhaust gases (with particulate material) to enter the DPF where the soot is trapped inside the filter, allowing cleaner exhaust gases to exit into the atmosphere, which then reduces the exhaust emissions from the engine. 

How long should A DPF Last?

A DPF filter should typically last for around 100,000 miles before needing to be replaced. The DPF's level of maintenance will have a big impact on how much this figure varies. While a well maintained DPF may even go 150,000 miles before needing to be replaced, a badly kept DPF; however, may last a much shorter time than the stated figure. To help extend the life and maintain performance of a DPF, a process known as ‘DPF regeneration’ can be used to clean the filter and restore its performance.


What Is DPF Regeneration?

DPF regeneration refers to the procedure of cleaning and emptying the diesel particulate filter of soot that is created by the process of combustion. Burning off the soot particles requires heating the diesel particulate filter to a very high temperature. Active regeneration or passive regeneration are the two methods that can be used to accomplish this. 

There are several factors that can affect the effectiveness of DPF regeneration, these are: 

  • The make of engine 
  • The type of DPF 
  • The driving conditions the vehicle has been put through 

For example, engines that are used primarily for short trips or in stop-and-go traffic may require more frequent regeneration to prevent the DPF from becoming clogged. Moreover, certain DPF systems are more likely than others to clog, meaning they may need maintenance more frequently. 


What Are The Types Of DPF Regeneration?

There are two main types of DPF regeneration: passive and active; however, DPF regeneration can be performed manually using a scan tool.  

Passive DPF regeneration occurs naturally during normal driving conditions when the temperature of the exhaust gas is high enough to burn off the particulate matter. However, this process is not always effective, especially for vehicles that are used for short trips or in cold weather conditions.  

Active DPF regeneration, on the other hand, is a more controlled process that is initiated by the engine control unit (ECU) when the DPF reaches a certain level of saturation. The ECU uses various sensors to monitor the exhaust gas temperature, pressure, and flow rate to determine when active regeneration is necessary. When the DPF is ready for regeneration, the ECU injects additional fuel into the engine to increase the temperature of the exhaust gas and initiate the cleaning process. 

During active regeneration, the temperature of the exhaust gas must reach a certain level to burn off the PM that has accumulated in the DPF. This temperature is typically around 1112 to 1292 Degrees Fahrenheit, which is much higher than the normal operating temperature of the engine. To achieve this, the engine may run in a high-idle mode or the vehicle may be driven at higher speeds for a period of time to increase the temperature of the exhaust gas. 

How to Regenerate a DPF manually

Manual regeneration is often required when vehicles are driven at insufficient speed to allow regeneration to be carried out automatically by their engine management control software. The vehicle is already suffering with driveability and lack of power problems. At this point, as long as the DPF is not severely blocked (over 90% capacity filled), a scan tool can be used to perform a static or  (up to 60% capacity filled) or dynamic regeneration to clear the soot levels in the DPF. 

Please see below an example of a dynamic DPF regeneration on a 2017 Mercedes using a Snap-on TRITON-D10: 

  1. Connect the scan tool to the vehicle's diagnostic port and follow the manufacturer's instructions for accessing the DPF regeneration function. 
  2. Ensure that the engine is fully warmed up and that the DPF is not excessively clogged. The scan tool may provide diagnostic information on the DPF's condition 
  3. Follow the prompts on the TRITON-D10 scan tool to initiate the manual regeneration process. This typically involves commanding the engine to run at a higher temperature to burn off the accumulated soot in the DPF. 

Screenshot of DPF Regeneration on a Mercedes

The image above shows a screenshot from the Snap-on TRITON-D10 during a dynamic DPF regeneration. Here, we can see the soot content going down and the fill level decreasing. The exhaust temperature reading sits between 1112F and 1292F. 

Monitor the regeneration process using the scan tool and ensure that the exhaust temperature does not exceed the manufacturer's specifications. If the temperature gets too high, the process may need to be aborted to prevent damage to the engine or the DPF. 

Once the regeneration process is complete, (a ‘Regeneration Successful’ message will show on the screen) the live data can be checked again to determine whether any additional work is required. 

The DPF regeneration is now complete. 

Please note: Some OE’s require a special function "Replace or Reset DPF" after the replacement of the filter. This can be found in the ‘Service Resets and Relearns’ menu. 

In conclusion, DPF regeneration is a critical procedure that lowers harmful emissions while maintaining the performance of diesel engines. While active regeneration is a more controlled process that is started by the engine control unit, passive regeneration happens naturally while driving normally. The temperature of the exhaust gas is raised during active regeneration in order to burn off the PM that has accumulated in the DPF. But to make sure the DPF keeps working well over time, proper maintenance is also required. This could involve performing a manual DPF regeneration detailed above, replacing the DPF filter entirely.