Diesel filter check added to MOT test

23rd January 2014

The testing of diesel cars, vans and lorries is being tightened up to ensure they have a critical exhaust filter.

From February, garages and testing stations will be required to check for diesel particulate filters when inspecting the exhaust system as part of the MOT (or annual test for heavy vehicles).  A vehicle will automatically fail if a filter has been fitted as Original Equipment but is found to no longer be present.

Particulate filters work by trapping solid matter from exhaust gases.  They have been in use for more than two decades and help diesel vehicles to meet EU emissions standards.  However they also need to be ‘regenerated’ regularly and, if not done properly, this can lead to a build up of soot, which can affect fuel economy. 

Consequently some diesel owners opt to remove them, which makes their vehicle illegal for road use.  It is an offence to drive a vehicle that has been modified this way, as it will no longer meet the standards it achieved when approved for sale in the UK initially.

“I am concerned that vehicles are being modified in a way that is detrimental to health and undoes the hard work car manufacturers have done to raise emissions standards,” Roads Minister Robert Goodwill said.  “This change to the MOT makes it clear – if you have this filter removed you will fail the test.”