What is a DPF?

A DPF (Diesel Particulate Filter) also known as FAP on some French vehicles, is a device fitted to the exhaust system of all diesel vehicles sold new from 2009 onwards when the Euro 5 standard came into force and made it compulsary (some makes of car have them pre 2009 in anticipation of the change in legislation). Its purpose is to reduce emissions and meet the stricter European emission standards. It does this by trapping soot (Particulate Matter – PM) from the exhaust gasses while letting the gasses flow through the system.

The particle filter reduces the pollution emitted by diesel vehicles by filtering the solid particles contained in the exhaust gases.

In time, the particle filter becomes clogged by accumulation of the following components:

  • Soot coming from the exhaust
  • Cinders arising from the engine oil
  • Particles coming from engine wear

As with any filter the DPF needs cleaning periodically to work efficiently. When the filter becomes clogged the vehicle’s ECU recognises this and initiates a process called regeneration. Regeneration consists of periodically burning off the particles accumulated in the particle filter  at a very high temperature turning it to ash and will occur naturally if the temperature of the exhaust gases is sufficiently high i.e when the vehicle is travelling at motorway speeds, or artificially by the ECU. By injecting an additional post injection fuel spray during the combustion process the ECU can raise the temperature of the exhaust gases aiding the burn off.


Why Problems Occur

In stop/start traffic or on short journeys a regeneration may not get time to complete, ideally you should be looking to drive 15-30 minutes at motorway speeds to enable the system to keep working as it should. If regeneration doesn’t function properly it leads to a build-up of soot which effects fuel economy and performance. Left unattended this will result in a Blocked DPF which can ultimately cause very expensive damage to other engine components and can even pose a fire risk. Even where regeneration is occurring correctly the soot left behind can also cause blockages over time so for this reason DPF’s are considered a serviceable item by manufacturers as brake pads and air filters are and so are not covered by any warranty. DPS’s need to be maintained in order to avoid costly repercussions to the vehicle.


What do I do if the DPF warning light comes on?

When your DPF warning light comes on please don’t ignore it, taking action early will help to avoid further damage to other components, additional repair bills and possible fire risks. Get professional advice as soon as possible and consider the following options available to resolve the problem.


What are the options?

By the time your DPF warning lights are visible your DPF will already be significantly blocked. Forced regeneration by a garage or a “blast down the motorway” is not likely to cure the problem, these only work as preventative maintenance. So at this stage realistically you have the following options. As a Quantum dealer we are able to offer;

DPF Regeneration

DPF Replacement – Normally at a fraction of the main dealer cost.

DPF Cleaning

DPF Recalibration – If you have had your DPF core removed, your Quantum dealer may be able to recalibrate your vehicles ECU to stop your engine going into limp-home mode and clear the DPF warning light. Consumers must be aware of the legal implications (as below) of this being carried out.

DPF Removal is legal in certain countries and when used for off-road or motorsport – if in any doubt please take advice.

The ideal DPF solution for you depends on your circumstances e.g. type & condition of your vehicle, your usage, your future plans i.e. whether you intend to keep or sell the vehicle etc and your budget.

Trade on-site support welcome.



From February 2014 the inspection of the exhaust system carried out during the MoT test will include a check for the presence of a DPF.

A missing DPF, where one was fitted when the vehicle was built, will result in an MoT failure. A vehicle might still pass the MoT visible smoke emissions test, which is primarily intended to identify vehicles that are in a very poor state of repair, whilst emitting illegal and harmful levels of fine exhaust particulate. It is an offence under the Road vehicles (Construction and Use) Regulations (Regulation 61a(3))1 to use a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet.

Removal of a DPF will almost invariably contravene these requirements, making the vehicle illegal for road use. The potential penalties for failing to comply are fines of up to £1,000 for a car or £2,500 for a light goods vehicle.