The diesel particulate filter traps soot from the exhaust before it reaches the atmosphere. It is a legal requirement on diesel vehicles from 2009 onwards. Remove it and the car will fail its MOT. The filter cleans itself during a process called regeneration, where exhaust temperatures rise high enough to burn the accumulated soot away. That regeneration needs a certain amount of sustained driving at speed to complete. Short, urban journeys at low speeds may never trigger it.
When the filter becomes too blocked to manage on its own, the DPF warning light appears. The filter is not broken at this point. In most cases it just needs a forced regeneration carried out by a technician with diagnostic equipment. We connect to the ECU, read the soot loading percentage, and command the engine management system to initiate a regen cycle. This costs £72 inc VAT and resolves the majority of DPF warning lights we see.
If that alone does not fully clear the blockage, the next approach is a chemical clean. A professional DPF cleaning chemical is introduced into the filter inlet and left to soak. An extended regeneration drive follows. The chemical helps break down the heavier deposits that the heat alone cannot shift. This option costs £144 inc VAT and is only used when the forced regen has been tried first.
For filters that are heavily blocked and have not responded to either of the above, physical removal and cleaning on our off-vehicle machine is the answer. Compressed air and cleaning fluid are used to flush the particulate matter through the substrate. This is the most thorough method available short of replacement. The £190+VAT machine clean cost covers the cleaning process itself. Removal and refitting is charged at the medium labour rate on top, because access to the DPF varies enormously between vehicles.
Replacement is reserved for filters that are physically cracked, damaged by a fuel injector fault, or contaminated by engine oil or coolant. These cannot be cleaned back to a usable condition. We will tell you honestly if that is the situation, provide a written quote, and wait for your approval before ordering any parts.
The best way to avoid DPF problems is a motorway run once a month. Twenty to thirty minutes on a dual carriageway or motorway at a reasonable speed is usually enough for a passive regen to complete. Using the correct engine oil specification also matters. Non-approved oils leave an ash residue in the filter that cannot be burned off.
