DPF cleaning and regeneration

Understanding Diesel Particulate Filters (DPF): Introduction and Common Faults


Since the introdution of Euro 5 emission standards (2009) Diesel Particulate Filters (DPFs) play a crucial role in reducing the environmental impact of diesel engines by capturing and trapping particulate matter (PM) emitted during combustion. PM consists of tiny particles, including soot and ash, which can be harmful to both human health and the environment. DPFs are designed to remove these particles, contributing to cleaner air and meeting stringent emission standards.

How DPFs Work:

DPFs operate through a process called filtration, which involves trapping and collecting particulate matter within the filter. The key components of a DPF include a ceramic or metal filter substrate and a regeneration system. As exhaust gases pass through the filter, particulate matter is trapped on the filter walls. To prevent clogging, the DPF periodically regenerates by burning off the collected soot.

There are two main types of regeneration:

Passive Regeneration: This occurs during normal driving conditions when the exhaust temperature is high enough to burn off the trapped soot.

Active Regeneration: In cases where passive regeneration is insufficient, the engine management system initiates active regeneration by increasing exhaust temperature through various means, such as injecting additional fuel into the exhaust stream.

Common DPF Faults:

Despite their crucial role, DPFs can experience various faults that impact their efficiency and performance. Understanding these common issues is essential for maintaining a properly functioning diesel engine.


  • Cause: Insufficient regeneration or short city trips preventing the DPF from reaching the required temperature for passive regeneration.
  • Symptoms: Reduced engine performance, increased fuel consumption, warning lights on the dashboard.
  • Solution: Regularly drive the vehicle at highway speeds to promote passive regeneration. Professional cleaning or replacement may be necessary if clogging persists.

Ash Accumulation:

  • Cause: Over time, ash from engine oil can accumulate in the DPF, reducing its effectiveness.
  • Symptoms: Similar to clogging, with potential long-term damage to the filter.
  • Solution: Periodic DPF cleaning or replacement to remove accumulated ash.

Faulty Sensors:

  • Cause: Malfunctioning temperature or pressure sensors can lead to incorrect readings and affect the regeneration process.
  • Symptoms: Inaccurate regeneration initiation, leading to increased soot accumulation.
  • Solution: Diagnose and replace faulty sensors to ensure accurate data for the engine management system.


Diesel Particulate Filter (DPF)

Diesel Exhaust Fluid (DEF)

Common DPF Faults:


Fuel Additive Issues:

  • Cause: Some vehicles require fuel additives such as diesel exhaust fluid (DEF) to aid in regeneration. Issues can arise if these additives are not used or topped up as recommended.
  • Symptoms: Incomplete regeneration, increased emissions, and DPF failure.
  • Solution: Follow the manufacturer's guidelines regarding the use of fuel additives to maintain proper DPF function.
DPF fault finding


Diesel Particulate Filters are essential for reducing the environmental impact of diesel engines. Regular maintenance, adherence to manufacturer guidelines, and understanding common faults are crucial for ensuring the longevity and effectiveness of DPFs. By addressing issues promptly, vehicle owners can contribute to cleaner air and meet emission standards maintaining optimal engine performance and reducing repair costs.

Blocked DPFs cause damaging back pressure on engines, oil dilution and eventual engine failure. Once the system has failed to automatically regenerate seek professional help.



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