New rules for diesel MoT tests
13 December 2013
Author: Will Stretton
New legislation has been introduced for MoT tests for diesel-engined vehicles.
From February 2014, testers will be required to check for a diesel particulate filter (DPF) in the exhaust system as part of the MOT, where one has been fitted to the vehicle as standard by the manufacturer.
If the filter is no longer present, then the vehicle will automatically fail the test.
DPFs are commonplace in modern diesel vehicles and help to curb particulate emissions, which in turn allows vehicles to meet European emissions standards and is said to improve air quality.
The Government has published a diesel particulate filter guidance [link: https://www.gov.uk/government/publications/diesel-particulate-filters-guidance-note] note to inform vehicle owners and operators of the changes to the MoT test.
The filters themselves have been said to cause reliability issues in the past.
This has prompted some firms to offer services to remove them claiming that such a modification will improve the vehicle's economy among other measures.
"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," said roads minister Robert Goodwill.
"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, 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."