Main Menu


    Unit 51 Youngs Industrial Estate
    Paices Hill
    RG7 4PW
    T: 0118 9810963


What is a Diesel Particulate Filter (DPF)?

A Diesel Particulate Filter, often referred to as the DPF is a device designed and integrated into the Diesel Engine exhaust systems to trap & remove Diesel Particulate Matter or Soot from the exhaust gasses of the diesel engine. Much like the Catalytic Converter of conventional petrol engines, the Diesel Particulate Filter works to remove harmful toxins and lower the emissions of your diesel engine making it more environmentally friendly. The aim is to remove 80% in the average diesel particulate (soot) emissions and although a great concept, it brings about a whole new line of problems. We're taking calls all day from anxious customers and garages across the country when their DPF (diesel particulate filter) light is illuminated on the dash, indicating that there is at least a partial blockage in the DPF system.

The problem with the Diesel Particulate Filter (DPF) System

The DPF works to trap & remove diesel particulate (soot) from the exhaust gasses of the diesel engine before it exits the exhaust. This is removed into the atmosphere, simply removed from the gasses that flow through the exhaust to help lower emissions. Imagine a DPF is like a honeycomb on the inside similar to the Catalytic Converter (CAT) of a petrol engine. As the gasses flow through it, the DPF will trap the harmful diesel particulate (soot) and with it's advanced technology break it down to remove as much of it as possible (between 80%-100%). The soot is burnt off at very high temperatures in the DPF and left behind is a very fine ash residue. The problem is this ash, it has no where to go and so will begin causing blockage in the DPF system. The ash & soot will partially block your DPF causing the DPF/CAT light to illuminate on the dash (normally when 45% blockage is reached) at which point regeneration is required to get the DPF back in to it's safety zone. Regeneration is the DPF's way to clear the blockage through continuously burning it at higher temperatures and allowing the now harmless produce to escape through the exhaust system. There are two types of Regeneration processes which will be explained further below. Sometimes the DPF light will appear on the dash intermittently, this does mean there is a partial blockage in your DPF and a regeneration process is required. You should make yourself aware of this process but many people are unsure or have no idea of this DPF system as it's still very new and not explained to everyone. If you bought your vehicle from new at a dealership, then this would have most likely been explained at the point of sale but in the second hand car trade, you can't expect this type of information to always be passed on. What happens is drivers see the light, then see it go off and ignore it - not knowing it's a partially blocked DPF. They continue to drive and again it will illuminate the DPF light on the dash and go off again but eventually it will stay on permanent and in most severe cases bring on the Engine management light and even the Coil Light which could start blinking. If this happens, you will lose all power and the vehicle will fall into "Limp Mode". This is the automatic reaction of the Engine Management ECU and if you're at this stage then unfortunately it will be a costly repair. You could be looking at having to replace the DPF unit and having your Engine Management ECU reprogrammed. A DPF replacement will cost you between £800 - £2,400 new (+Labour) from main dealers, depending on the Make & Model of your vehicle and the corresponding part numbers of the unit. Resetting the ECU light will cost you a further £45-100 and then you will have to be on the lookout for the next time the DPF light comes on to take the appropriate action to ensure the damage is not done all over again as if you fail to act, then you could potentially void any warranty given with the new DPF unit costing you double.

Passive & Active DPF Regeneration

What is Passive Regeneration?

Passive regeneration is an automated regeneration which often occurs on drives where there is prolonged high exhaust temperatures like for example on motorway-type runs, but it can't be said that all cars get the required long journey motorway-type trips necessary to complete a passive regeneration of the DPF system and so manufacturers have had to adapt the technology and design-in an "active" regeneration process controlled by the Engine Management Computer also known as the Engine Control Module (ECM).

What is Active Regeneration?

When the diesel particulate (soot) loading in the diesel particulate filter (DPF) reaches a pre-set limit (normally around 45%), the ECU will make minor adjustments to the fuel injection timing system which will in turn increase the exhaust temperatures and help initiate the DPF regeneration process. This is a smart way of getting a motorway-type temperature to build up inside the DPF system and begin a full regeneration to bring the unit back to good health, however, if the journey is a bit stop/start where you're in a built up city with traffic then the chances are the regeneration will not complete and eventually the DPF light will illuminate on the dash to tell you that the DPF system is partially blocked. At this point it is recommended that you try to find time to complete a full regeneration and this can be done on a simple 10 minutes or so drive of speeds above 40mph. If you do not do this and choose to ignore the light, it may go out but come back on and as you continue in a relatively slow, stop/start pattern of driving the soot loading will continue to build up and clog up the DPF system until it reaches closer to 75% blocked at which point you can expect other more serious warning lights to appear on the dashboard. By now, driving at speed alone will no longer be sufficient and the car will need to go to a specialised garage such as SEDOX or a dealership for regeneration. The other lights may be the engine management light constantly on & possibly even the glow plug light blinking constantly. It is not advised to continue driving the vehicle under these conditions to avoid further costly damages to the DPF system and other mechanical components. Common Vehicles Suffering the DPF System Failure Problems The DPF system is fitted to a wide range of cars and in fact is being installed on almost all new Diesel engines so the problem will in future become more and more common, however, at this moment in time we've put together a small list of the most common cars which we're having to deal with on a weekly basis suffering from the DPF system problems:

  • Alfa Romeo Diesel Particulate Filter (DPF) problems
  • Audi - 1.4 TDI, 1.9 TDI, 2.0 TDI, 2.5 TDI, 2.7 TDI, 3.0 TDI, 4.2 TDI, 5.0 TDI etc. Diesel Particulate Filter (DPF) problems
  • BMW & Mini Diesel Particulate Filter (DPF) problems
  • Citroen Diesel Particulate Filter (DPF) problems
  • Chevrolet Diesel Particulate Filter (DPF) problems
  • Fiat Diesel Particulate Filter (DPF) problems
  • Ford Diesel Particulate Filter (DPF) problems
  • Honda Diesel Particulate Filter (DPF) problems
  • Hyundai Diesel Particulate Filter (DPF) problems
  • Jaguar Diesel Particulate Filter (DPF) problems
  • Kia Diesel Particulate Filter (DPF) problems
  • Lancia Diesel Particulate Filter (DPF) problems
  • Mazda Diesel Particulate Filter (DPF) problems
  • Mercedes Diesel Particulate Filter (DPF) problems
  • Nissan Diesel Particulate Filter (DPF) problems
  • Opel Diesel Particulate Filter (DPF) problems
  • Peugeot Diesel Particulate Filter (DPF) problems
  • Renault Diesel Particulate Filter (DPF) problems
  • Rover Diesel Particulate Filter (DPF) problems
  • Saab Diesel Particulate Filter (DPF) problems
  • Seat Diesel Particulate Filter (DPF) problems
  • Skoda Diesel Particulate Filter (DPF) problems
  • Toyota Diesel Particulate Filter (DPF) problems
  • Vauxhall Diesel Particulate Filter (DPF) problems
  • Volkswagen Diesel Particulate Filter (DPF) problems
  • Volvo Diesel Particulate Filter (DPF) problems