What is a diesel particulate filter?

They are becoming more and more common on diesel engines. They are designed to reduce the exhaust emissions as required by European legislation, especially particulate matter. A particle filter traps most of the soot that is produced by diesel fuel combustion that would normally travel down the exhaust and into the atmosphere.

Why does the filter need to ‘regenerate’?

The filter can hold a certain amount of soot but not a high quantity, so it needs to regularly go through the process of regeneration in order to clear out the soot and allow the vehicle to operate properly. Regeneration occurs when the filter reaches a sufficiently high temperature to convert the stored soot into a much finer ash.

To allow the filter to automatically regenerate, the vehicle should be used regularly at a sufficient speed to ensure a high enough temperature of the exhaust gas.

Although this varies from manufacturer to manufacturer, typically a vehicle must be driven at least at 50mph or above for a minimum of 20 minutes to raise the temperature in the exhaust sufficiently to engage automatic regeneration.

What happens if it doesn’t regenerate?

If the vehicle is not driven in such a way that automatically regenerates the particulate filter, it will build up with an excessive amount of soot, that if not resolved, will reduce the performance of the vehicle and damage the filter.

If the filter builds up too much soot, a warning light on the dashboard will alert you. Typically the problem can be resolved by driving in accordance with the manufacturer guidelines on automatic regeneration, ie. Driving at a speed and distance sufficient to heat the exhaust sufficiently.

If this automatic regeneration is not possible due to traffic conditions or speed limits the vehicle may need a forced regeneration by a garage in order to clear the filter. If the warning light is ignored and the filter is not regenerated, it will cause damage to the vehicle.

Vehicles with diesel particulate filters

The majority of vehicle manufacturers now have diesel particulate filters as a standard fitment but not all diesel models, for specific details of individual models, you should refer to the manufacturer’s website.

For advice, please contact the workshop direct on 01926 495211