Diesel Particulate Filters to be Tested in MoT from February

Published 06 December 2013

As Honest John has frequently warned, removal of a Diesel Particulate filter has always been illegal under EC law. Now VOSA has announced that garages and testing stations will be required check for a diesel particulate filter (DPF) in the inspection of the exhaust system as part of the MoT test (or annual test for heavy vehicles) from February 2014.

The vehicle will automatically fail the MoT test if a DPF was originally fitted as standard but is found to be no longer present.

(Obviously if no DPF was ever fitted in the case of EUIII and many EUIV vehicles, the vehicle will not fail for not having one.)

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 boost consumption. 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.

Roads Minister Robert Goodwill 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."

The 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 and ash, 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.

DPFs of HGVs are regularly cleaned by the Ceramex process that restores their functionality to more than 90%, and this service is now being offered to car owners via Unipart and Alliance Car Centres and is on trial at six branches of KwikFit.

More information can be found via the Diesel particulate filters guidance note that will be updated to reflect the changes to the MoT test.


Marnold2452    on 6 December 2013

If the DPF has been opened and the insides removed then welded back together to the tester it will still be fitted. How will the MOT spot this modification?

Triffid    on 8 December 2013

There will be smoke particles. Don't waste your time in trying to fool the MOT tester, they will know what to look for. A lot of dpf removal companies remove not just the dpf but some of the other attached bits with keep it in place and lubricated. With the proper mapping software needed as well you'll be looking at anything from 2 to 3k at a main dealer I bet.

co2blues    on 9 December 2013

Instead of wielding the traditional "Big Stick" wouldn't it be better if the great british government issued guidance on how motorists (the people who donate so generously to HMG revenues) could combat the build up and ultimate failure of DPFs ?
I thought they were going to be less motorist hating !

marcos    on 10 December 2013

Simple, Avoid antisocial polluting diesels altogether then you won't have to concern yourself with DPF problems.

pmbbiggsy    on 11 December 2013

Another clueless govt minister and commenters. DPFs were fitted to some vehicles before it was a legal requirement - so if they pass the relevant emissions test with the filter removed then what's the problem? DPFs are a big problem on some cars because they are unable to regenerate during normal driving, so then you have to drive for 15 minutes keeping the revs at 2000rpm, whether you want to make the journey or not! How is that environmentally friendly? How much extra fuel is burned to keep the DPF at 650C? What are the emissions like during a regen????

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