Removal of DPF Filters and the MOT
Diesel Particulate Filters need to be emptied of trapped particulate matter regularly. This is done by regeneration, which involves burning the soot at a very high temperature, leaving behind only a very small residue. Regeneration, If not carried out properly, can lead to a build up of soot which can affect performance and ultimately lead to expensive repair costs. This has led to some diesel vehicle owners removing their DPFS. However, DPF removal has both legal and social implications.
The DPF filters need to be ‘regenerated’ regularly through burning the soot to gas at a very high temperature, leaving behind a residue. If not carried out properly, regeneration can lead to a build-up of soot, which can affect performance. This has led to some diesel vehicle owners opting to remove the filter, which makes their car illegal for road use.
The filter works by trapping solid particulate matter from exhaust gases. This type of filter has been in use for more than 20 years and helps meet European emission standards, improving air quality and health standards.
Some firms offer services to remove the filter, claiming it will improve the economy. But it is an offence to drive a vehicle that has been modified this way, as it will no longer meet the emissions standards the car achieved when it was approved for sale in the UK.
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 with Regulation 61a are fines of up to £1,000 for a car or £2,500 for a light goods vehicle.
However, until 16th February 2014 the DPF filter on diesel vehicles was not checked during MOT Testing. This was added to the test after a statement made by the then Roads Minister, Robert Goodwill, in December 2013 who said:-
“I am very concerned that vehicles are being modified in a way that is clearly detrimental to people’s health and undoes the hard work car manufacturers have taken to improve emissions standards. It has become apparent the government had to intervene to clarify the position on particulate filter removal given the unacceptable negative impact on air quality.
This change to the MOT tests makes it clear – if you have this filter removed from your car it will fail the test.”
This resulted in the current situation where there is now a MOT reason for rejection of:-
“…….A catalytic converter or particulate filter missing where one was fitted as standard”
The tester though can only fail if it is clear that the filter is missing and there was one fitted as standard.
In reality a tester will face the situation where they are not sure if one was fitted as standard and there is no data available that can confirm one way or another what was fitted as standard. Alternatively the Tester will see the DPF case present and connected but with possibly welds showing that at some stage the case has been cut in two.
The tester may presume that this means the internals of the filter have been removed, but would not be able to prove it.
As always in this situation where the tester is not 100% certain that a failure exists then the correct course of action would be to pass and advise.
It would be a great help if there was an accurate database of which vehicles were fitted with DPF filters as standard, and there has been talk of tighter smoke test values for DPF equipped vehicles to help ensure the DPF is functioning. We have spoken to the DVSA on this matter and this is something that would be looked at when time allows by the Department of Transport.
The DVSA though are tackling the possible illegal removal of DPF filters another way though, by issuing through a special notice to MOT stations (6-14) stating an aim to take action against any business that is authorised for MOT testing, who also offers a DPF removal service outside the MOT.
“.. The DPF plays an essential environmental role in enabling reductions in emissions which help meet strict European emission standards, reducing air pollution and thereby improving health quality. DVSA are aware of an increasing number of businesses offering a service to remove or bypass the DPF. This practice compromises the MOT testing standards and therefore undermines the principle of inspecting their presence. Authorised Examiners are responsible to ensure that MOT Testing is carried out to the required standards. Where a VTS is offering a service which could undermine this (such as removing or bypassing DPFs) DVSA will consider this as bringing the MOT Scheme into disrepute. Where the scheme is brought into disrepute DVSA may consider taking action to remove the Authorisation if appropriate.”
Head of MOT Technical Operations
20 July 2016