The “active regeneration” process is usually a limit programmed into the vehicles ECU. Once the DPF reaches this level of soot, the exhaust temperature is automatically raised. However, most urban journeys are often shorter than the time needed to complete the active regeneration process, and if it's interrupted too often, issues can occur. The best way to maintain a DPF is to ensure that it’s able to regenerate itself properly. The majority of DPF problems occur when this process is interrupted! Faulty turbochargers and faulty injectors can also cause issues with a DPF.