DPF removal gutting MOT test fail pass diesel particulate filter

Surprisingly, DPF related googling now accounts for the vast majority of the traffic to Hypermiler. Therefore we are always looking to expand our library of DPF information for all our knowledge thirsty visitors.

One of the hottest topics of late is the effect removing or gutting your DPF (Diesel Particulate Filter) will have on your vehicle’s ability to pass its MOT test.

I am very lucky to have a close friend who is an MOT inspector, he was able to fill us in on some rather surprising information. We’re not going to name our source, but he was happy to answer the following questions.

Will my car fail its MOT if I remove my DFP Diesel Particulate Filter?

Yes. From Feburary 2014 MOT testers are required to check for a the presence of a DPF filter. If it’s gone, so are your chances of an MOT pass. Here’s the official line from the Gov.uk website (here)

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 the filter had been fitted as standard but is found to be no longer present

The above is not to say your local MOT tester might turn a blind eye or notice that your DPF has vanished, but if he’s doing his job correctly your car will fail.

Will my car fail it’s MOT if I have the DFP Diesel Particulate Filter gutted?

Now this is the interesting part, what happens if your DFP Diesel Particulate filter gutted?

This process involves cutting open the filter, removing the internal filter matter and welding it back up. Without the filter in place there is very little to capture your diesel particulate matter and even less to get clogged. But will it pass it’s MOT?

Our man, begrudgingly says YES! Even with signs that the device has been “tampered” with, they can not fail the vehicle as long as it meets emission regulations. In his words, they “must give you the benefit of the doubt, the most you can get is an advisory”.

Before you go reaching for the angle grinder and welding mask were sorry to say that its not quite that simple. If you do take the drastic step of removing the intermal “gubbins” from the filter you will need to have the ECU modified to remove the DPF sensor warning system. This often called remapping and will disable the DPF part of your vehicles ECU (brain) and in most cases provide you with a nice increase in performance. This has to be done by a specialist – google is your friend.


We’ve been recently made aware that the government and VOSA are very aware of the legal and environmental issues surrounding DPF removal. At present the MOT test CAN NOT detect that your DPF has been gutted / removed or tampered with but…. changes are afoot.

We have been reliably informed that the MOT test will soon be changing to include a test for diesel particulates and soot. This test measure the effectiveness of your DPF and your vehicle will fail it’s MOT if you’ve been naughty.

It’s still very early days but please be careful when considering the removal of your DPF filter.


A word of warning

Like you, I’ve been bitten by DPF issues, my Nissan Qashqai DPF had to be dealer regenerated a number of times, costing in excess of £900 alone. DPF filters are there for a reason, they are designed to improve your dirty oil burners emissions and help improve air quality. We certainly don’t condone the removal of your DPF filter but we fully understand your frustration with the bloody things!

For more information on DPFs you might also like to check out the following pages

If you’re having DPF related issues please leave a comment below and we (or another visitor) might just be able to steer you in the right path.