A Diesel Particulate Filter (DPF) is an emission reduction filter that, under certain laws throughout the world, must be fitted to diesel vehicles. It is used to remove deadly gases and harmful particles produced by diesel exhaust fumes. Excess soot can also form due to poor servicing, incorrect oil use, poor fuel quality and unsuitable driving habits.

The DPF is designed to capture these particles and then be regenerated, or cleaned, via high-temperature burns. It is when this regeneration process does not happen that the filter becomes clogged, causing problems to arise. The diesel particulate filter is often portrayed as an expensive component that must be replaced, however, in many cases this is not necessary.

When diagnosed and maintained correctly, a DPF replacement can be avoided.

When a DPF fault code is present in the engine’s computer, or a warning light appears on the dashboard, it does not necessarily mean the DPF is blocked. You may encounter unusual symptoms; however, this does not necessarily mean a major repair. In fact, some simple service items may be sufficient to resolve the issue.

• Surging, jerking, or a noticeable decline in performance while driving
• High fuel consumption leading to poor fuel economy
• Excessive smoke; colors such as white, blue, or black
• Engine and/or DPF emissions warning lights displayed
• Difficulty starting the engine
• The engine runs rough
• Unsuccessful attempts at regeneration
• Rattling or knocking sounds from the engine
• A loud whistle or hissing noise whilst driving

The vehicle's computer utilises embedded algorithms to perform regular regenerations, also known as burns. This process increases the temperature in the exhaust to burn away the particles and soot collected in the filter. During regeneration, you may notice a temporary change in exhaust smell or temperature. Continuous smoke, however, may indicate an underlying issue.

If another component is malfunctioning, regeneration may occur more frequently — or stop entirely — until the underlying fault is rectified.

• Service your vehicle according to the manufacturer's maintenance schedule - avoid late services
• Ensure the correct oils are used
• Do not drive with any faults in your car - do not ignore dashboard warning lights
• Avoid using poor quality fuel
• Do not attempt to resolve DPF issues without proper diagnosis
• Modify your vehicle with caution
• Limit excessive idling; increase the RPM to between 1800 and 2200. To enable this, drop down a gear, especially in slow-moving traffic
• Notify your mechanic about any changes or symptoms with your vehicle, such as louder whistles, hissing noise or a jerking feel whilst driving
• Ensure your mechanic is experienced in diagnosing modern diesel emission systems. We can refer you to an independent workshop that is part of the Diesel Help technical support network.

Component failures that trigger DPF-related symptoms do not necessarily mean the filter itself requires replacement. With correct diagnosis and guidance, your mechanic should be able to rectify the underlying cause without unnecessary replacement. We have developed the vehicle owner's guide, which outlines Common Diesel Problems Explained, that you will find helpful.

A well-maintained Diesel Particulate Filter can often last well over 200,000 kilometres before replacement is required. In many cases, once the underlying cause is rectified, the DPF may simply need cleaning. This can be done on the vehicle, or in extreme cases, the DPF will be removed and sent away to a professional DPF cleaning service. Any work on the DPF must be performed by a qualified and experienced mechanic.

Determining whether a DPF is internally damaged, melted or heavily blocked requires professional inspection and testing.

In some cases, professional DPF cleaning services may restore the filter once the underlying cause has been corrected.

Final Advice for Diesel Owners

A DPF warning light does not automatically mean replacement is required. In many cases, correct servicing and proper diagnosis can restore normal operation.

Diesel Help Australia works exclusively with professional workshops.
If you require diagnosis or repair, we can refer you to an independent workshop that is part of the Diesel Help technical support network.

Return to the Diesel Vehicle Owner’s Guide for more topics and maintenance information.