Diesel Particulate Filter Removal, and the MOT

Cat Core Removal

Diesel particulate filters – and the MOT

[Please note that MOT Test regulations have changed since this article was first posted – see below for revised regulations]

In late September, a Labour Peer in the House of Lords, Lord Berkeley, asked the Government what on the face of it was a simple question:

“what steps they are taking to warn vehicle owners of any legal consequences resulting from the operation of vehicles from which factory-fitted diesel particulate filters have been removed.”

A Liberal Democrat Peer, Lord Newby responded on behalf of the Government:

“Diesel particulate filters are inspected visually at the annual MOT. Removal of the diesel particulate filter might trigger the vehicle’s Malfunction Indicator Lamp and the MOT Tester would bring this to the attention of the owner but the vehicle would not fail the MOT Test. Also, if the visual inspection indicated that the filter was missing, the Tester would inform the owner, but again the vehicle would not fail the MOT Test unless it failed the emissions test. However, the Department for Transport does not record information on the number of filters that have been removed from vehicles.

The Department does not currently provide information or advice to vehicle owners of any legal implications of removing these filters. However, Departmental officials are working on a guidance note that aims to provide vehicle owners with relevant information on the consequences of removing the filters. Nevertheless, officials will give appropriate advice either verbally or in writing when questions arise.”

Not Checked
Whilst checking diesel EMISSIONS is part of the MOT, in fact, as Lord Newby points out – the particulate filter itself is not checked during the MOT – and his statement that “Diesel particulate filters are inspected visually at the annual MOT”, is not correct. In fact an MOT Tester would not necessarily know whether a particulate filter was a standard fitting on any specific vehicle or not. That being the case, the situation where an MOT Tester would bring a missing particulate filter to the attention of a customer would be very unlikely to arise.

What has happened here is that the correct answer to the question is that there are NO legal consequences if the particulate filter has been removed and that is an embarrassment to the Government. So it looks as if the MOT has been used as a ‘smokescreen’ to disguise the fact that there’s a very simple answer to the question, which should have been “There aren’t any…”. A pity he couldn’t get his MOT facts right…

Since this article was posted the latest MOT inspections of the DPFs for diesel engined vehicles have changed and are currently as follows:

8.2.2 Compression ignition engine emissions Exhaust emission control equipment

You only need to check components that are visible and identifiable, such as diesel oxidation catalysts, diesel particulate filters, exhaust gas recirculation valves and selective catalytic reduction valves.

If a diesel particulate filter has clearly been cut open and rewelded, you should reject it unless the vehicle presenter can show evidence that there was a valid reason to cut it open, such as for filter cleaning.

  1. Emission control equipment fitted by the manufacturer missing, obviously modified or obviously defective
  1. An induction or exhaust leak that could affect emissions levels
  1. Evidence that the diesel particulate filter has been tampered with

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