All diesel cars that were manufactured after 2009 have a DPF fitted (Diesel Particulate Filter). The idea is that the filter collects the exhaust soot in order to reduce emissions. As this soot builds up the DPF will carry out what is called a regeneration to burn up the soot in to harmless waste and expel it out the exhaust of the vehicle.
A DPF can fail for many reasons. If the car has not been driven for long periods of time when the engine can get warm, if it is stood idling for a long time or driven on short journeys or slowly then the regenerate process may not happen. If too much soot has already accumulated then this is another reason why the regenerate process may not be able to be completed. You can take your car to a garage where they have a diagnostic machine. The machine will be able to tell them when the last regenerate was and whether it was successful. If it wasn’t they may be able to force it to do a manual regeneration. It may be that the DPF needs to be professionally cleaned before it will start to regenerate itself again properly.
