DPF regeneration is a process where the Diesel Particulate Filter gets rid of the build-up of soot that is the result of the diesel fuel combustion process – it effectively self-cleans. There are three types of DPF regeneration: passive, active, and forced. As the name implies, passive regeneration takes place during normal driving. Regeneration of the DPF is dependent on temperatures being sufficiently high to ‘burn off’ the soot that has built up on the filter walls and if those temperatures are reached during a normal drive-cycle, then regeneration will take place.
However, if sufficient temperatures are not reached because of driving style or journey type, then active regeneration will occur. With active regeneration, a metered addition of fuel is added into either exhaust stream, downstream of the turbo, or directly into the engine cylinders on the exhaust stroke via the fuel injection system. This mix of fuel and exhaust gas create the temperatures required to burn off the built-up soot.
If this form of regeneration doesn’t work, then a forced regeneration will be required. A forced regeneration is normally done at a garage and they will use a computer program to perform a manual forced regeneration. On some vehicles a dashboard mounted switch alongside several different signal interlocks e.g. transmission in neutral, hand brake on, engine coolant temperature being in place can also initiate a forced regeneration.