DPF, EGR and AdBlue Deletes: The MOT and UK Law

What UK Law Says About Emissions Equipment

Regulation 61A of the Road Vehicles (Construction and Use) Regulations 1986 sets emissions standards for vehicles used on a road. Two parts matter here. The vehicle must not fail its limits because of 'an alteration to the propulsion unit or exhaust system', and any device fitted to control emissions must be kept 'in good and efficient working order'. A DPF, an EGR valve and an AdBlue (SCR) system are all devices of that kind.

The Department for Transport's guidance note on diesel particulate filters says removing a DPF 'will almost invariably contravene these requirements, making the vehicle illegal for road use', and that the penalties are fines of up to £1,000 for a car or £2,500 for a light goods vehicle. The same logic applies to a disabled EGR or AdBlue system, because each is emissions equipment the vehicle was approved with.

What The MOT Tester Checks On A Diesel

The MOT has checked for the presence of a DPF since February 2014, and DVSA told testers that a vehicle built with one and presented without it should fail. On 20 May 2018 the rules tightened: visible smoke of any colour from a DPF-equipped diesel became a major fault, and so did any evidence that the DPF has been tampered with. A DPF can that has been cut open and rewelded is rejected unless the owner can show a valid reason, such as a filter clean.

EGR and AdBlue Deletes At The MOT

The MOT manual does not have a separate line for EGR or AdBlue. Both fall under 'emission control equipment fitted by the manufacturer missing, obviously modified or obviously defective', which is a major fault if the tester can see it. An AdBlue fluid leak on its own is not a reason for failure.

A delete done in software is written so the engine warning light stays off, which is why the visual check and the smoke test carry the weight at the MOT. That does not make a deleted road vehicle legal. The MOT is a check on one day; regulation 61A applies every time the vehicle is used on a road, and DVSA has described passing a vehicle known to have its DPF missing as fraud.

Roadside Checks On AdBlue Emulators

Enforcement is not limited to the MOT. DVSA ran a pilot at five sites in 2017 and 2018, checked 20,986 heavy vehicles for AdBlue emulators, and found 449. It began nationwide checks from September 2018. Operators caught with one get a prohibition and a short deadline to remove it, and at least one operator's licence has been revoked over an emulator. Those checks target lorries and coaches, but they show how the authorities view a disabled AdBlue system.

Deletes and Your Insurance

DVSA has warned that removing a DPF can invalidate a vehicle's insurance. Any delete is a modification, and the Financial Ombudsman Service has backed insurers who voided policies over undeclared engine modifications. For a vehicle that never goes on a public road, check what cover it has and tell that insurer about the change. Our guide on remaps and insurance explains what insurers can do when a modification is not declared.

Where A Delete Is Legal: Off-Road, Competition, Agricultural and Export

The road rules apply to vehicles used on a road. A vehicle that is not, or that is leaving the UK, is in a different position. These are the uses deletes are sold for:

• Off-road vehicles used only on private land, such as site vehicles, farm yards and private estates.
• Competition vehicles: track, rally, drag and other motorsport cars that are trailered to events.
• Agricultural machinery and plant that works off the public road.
• Export vehicles leaving the UK, where the rules of the country they go to then apply, so check them first.

Our Deletes, and What We Do For Road Vehicles

We carry out DPF delete remaps (from £185), EGR delete remaps (from £195, or £255 for both) and AdBlue delete remaps (from £285) for off-road, competition, agricultural and export vehicles, at the vehicle. The details for each are on the DPF delete, EGR delete and AdBlue delete service pages.

For a car or van that stays on the road with a blocked DPF, the answer is a clean, not a delete. Our mobile DPF cleaning starts from £195: diagnostics first, a high-pressure chemical clean, then a recheck, usually 45 to 60 minutes on site. On a Mercedes Sprinter in St Helens with 120% soot load and limp mode, we found 2 of the 3 exhaust temperature sensors dead, cleaned the filter on site with foam, and the owner booked the sensors in for the next day.