All diesel cars manufactured after 2009 had to be fitted with a DPF (Diesel Particulate Filter). This filter is designed to reduce the amount of harmful material that is released into the air. As you drive along the diesel engine will produce soot. This soot can get into people’s lungs and can cause health issues so the diesel particulate filter has been installed to collect this soot. When the filter becomes full, it will try and do what is known as a regeneration. This requires the engine to be running at a high revs for a certain amount of time for it to be able to get hot enough to burn up the soot in to ash.
Problems can arise with the DPF if it is not driven on long journeys from time to time as the regen process may not be able to be completed. If this happens a few times it could clog up the filter and you may get a warning light illuminate on your dash. The first warning you may get is a light telling you that a regen is needed. At this point take the car out for a decent drive on a motorway for a good 30 mins to get it to regen. Try and keep the revs high by driving in a lower gear. This should be enough to clear it out. If this does not happen you may then get a warning to say that the DPF needs to be checked or is clogged. At this point it will need to go into a garage to get them to sort it out for you.