Thousands of UK drivers flouting law by having diesel particulate filters removed

30 October 2017

Thousands of UK drivers flouting law by having diesel particulate filters removed

30 October 2017

A new investigation has revealed that a large number of UK motorists are breaking the law by driving cars with their diesel particulate filters (DPF) removed.

Since 2014, the country’s MOT laws have stated that in order for a vehicle to achieve a pass, it must have a DPF in place, should one have been fitted as standard. The filter reduces nitrogen oxide (NOx) emissions by trapping them, then burning them off harmlessly when it reaches a certain temperature, known as a ‘regeneration’.

However, diesel drivers who rarely use motorways or make long trips find that their DPF becomes clogged, which can lead to performance issues. Rather than have them professionally cleaned, or at worst replaced, some are seeking garages that can remove the innards of the filter, leaving the can section in place. As the MOT for diesel cars only involves a visual check, and a smoke emissions test rather than recording levels of CO2 and NOx, many are able to get away with such removal.

According to an investigation by the BBC, the Driver and Vehicle Standards Agency (DVSA) states that 1,800 cars in the country have been failed for not having a DPF in place during the MOT, but believes there are thousands more still on the road. The government body has said it plans to introduce changes to the annual test in 2018 as a result.

The BBC followed the progress of a car which had its filter removed through MOT tests at three different garages. Mechanics failed to spot the filter had been taken out on each occasion.

Frank Kelly, professor of environmental health at Kings College, London, said the health impact was devastating. ‘If a DPF is removed, it takes the work being done to restrict emissions back 30 years. A car with a DPF removed has a particulate count 20 times higher than one with it,’ he told the BBC. ‘The particles lead to numerous health problems such as lung cancer, heart attacks, strokes, Parkinson's, Alzheimer's - and can also affect an unborn child in the womb.’

Nick Molden, chief executive of Emissions Analytics, commented: ‘It is clear a more detailed inspection of vehicles is required during MOT, and potentially spot-checking of vehicles in real world situations is needed, too. The MOT test is clearly not fit for purpose in checking if a DPF has been removed.’

While introducing an emission test for diesel vehicles at the MOT may prove to be cost inhibitive, due to different metres being required, one way to detect whether a DPF has been removed is through the OBDII port. Once a filter is removed, the vehicle ECU needs to be reprogrammed to prevent any engine or DPF light coming on. If such programming is detected, a vehicle could be failed.

A spokesman for the Driver and Vehicle Standards Agency said: ‘DVSA is making further changes to the MOT manual and to the diesel emissions limits for modern vehicles, in May 2018. These will make the test more robust and better able to detect where emissions control equipment has been tampered with.’