From February 16th 2014, any diesel vehicle that had a diesel particulate filter (DPF) or diesel catalytic converter (DCAT) fitted as standard will fail an MOT test if that filter has been removed.

DPFs are fitted to filter out diesel particulate from exhaust gasses. They sometimes need a ‘regeneration’ to clear them of particle build up, which involves a fairly lengthy drive, at speed, to get the filter hot for 10 to 20 minutes or more. Doing this is a normal part of the car’s regular maintenance routine – if you don’t know how to regenerate your car’s DPF, consult the car’s handbook.

If the regeneration isn’t done when the warning light comes on, or doesn’t get hot enough for long enough to regenerate properly, further help might be required by getting the filter cleaned professionally. Not maintaining the filter can cause it to fail, resulting in a costly replacement bill!

Some people have opted to get the filter removed instead of maintaining it. However from this month, missing filters will be an MOT failure if they were fitted as standard to that car – plus there is the risk of a pretty hefty fine.