Drive a Modern Diesel?

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By Darren Hood, RAC Development Specialist on 16 December 2009 at 13:18

If you are driving a diesel vehicle built within the last 3 years the chances are it has a Diesel Particulate Filter (DPF) fitted. What does the DPF do? How does it work? How does it affect me? What are the common problems

To conform to modern exhaust emission standards almost all late diesel engines in production have a DPF fitted within the exhaust system.

So what does the DPF do?

The DPF traps the soot that is produced when the engine is running, which would normally pass through the exhaust system and enter the atmosphere.

How does it work?

The exhaust gases pass through the DPF, which traps the soot particles. The DPF continues to collect these soot particles until the filter is full. To clear the soot particles from the filter, the DPF uses a process called regeneration. The regeneration process increases the temperature within the DPF and burns off the soot particles.

How does it affect me?

For most vehicles the regeneration process takes place automatically without the driver knowing.

If the vehicle is continually used for short stop – start journeys the system may not be able to automatically regenerate and a warning light or message will appear to alert the driver. In most cases this warning light means the vehicle needs help to carry out DPF regeneration, which can involve driving continuously for about 5-40 minutes.

The owner’s manual describes what specific actions are required when the warning light is illuminated.

What are the common problems?

RAC attend a number of vehicles where the DPF warning light has been ignored. Ignoring this warning light can cause reduced performance and in some cases expensive consequential damage to the DPF and engine components.