Many modern diesel car owners ask us, “what is a DPF?”

The diesel particulate filter, more commonly referred to as the DPF or FAP, is a particle filter specially designed for modern diesel engines. This is similar to a Catalytic Converter found on many petrol engines which lowers emissions, but works in a different manner.

The DPF is designed to reduce pollution by filtering out solid soot particles. As the exhaust gases from the engine flow through it. Manufacturers claim 75%-85% of the soot particles are removed and held within the filter. The problem is the particles removed from the gases don’t always break down efficiently and when there is a specified amount held within the filter the ECU will begin a process called passive regeneration. Even once a regeneration cycle has taken place not all the soot particles will be removed, a proportion of them will just become smaller and make a finer dust which will inevitably block the filter further over time. To help improve this, a second stage of regeneration will begin, this is called active regeneration and will usually show at least one warning light on the dashboard of the vehicle. Your ECU will cause the engine to raise exhaust gas temperatures to 600-700°C for about 20 minutes to burn off the build up of excess residue. If your journey means that the regeneration process cant complete its full cycle ie the vehicle is not driven to manufacturers guidelines and this happens over 2-3 journeys then the soot that is being collected and is now dramatically increasing due to the regeneration process will then trigger further warning lights on the dashboard. If it continues to increase without a successful regeneration the vehicle may well experience a loss of power also known as limp mode. By this point the DPF will need to be replaced or removed.