Catalytic converters and diesel particulate filters
Updated 30 May 2023
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This guidance explains the rules that apply to the manufacture, sale and fitting of catalytic converters and diesel particulate filters.
Catalytic converters
Vehicles registered after March 2001
Fitting a catalytic converter
If you install a catalytic converter on a vehicle registered on or after 1 March 2001, you must check that it is type-approved.
Read the section of this guidance on checking type approval.
Supplying a catalytic converter
It is illegal to supply catalytic converters that are not type-approved for use on vehicles registered after 1 March 2001.
Vehicles registered before March 2001
If your vehicle is first registered before 1 March 2001, replacement catalytic converters do not need to be type-approved. The replacement should provide an equivalent level of performance to the original catalytic converter.
Diesel particulate filters
Vehicles registered after January 2011
Fitting a diesel particulate filter
If you install a diesel particulate filter (DPF) on a vehicle that is Euro 5 or above, you must check that the DPF is type-approved.
Euro 5 applies to vehicles registered on or after 1 January 2011, though some Euro 5 vehicles were registered before this date.
Read the section of this guidance on checking type approval.
You can fit a DPF that is not type-approved to earlier vehicles - Euro 4 and below.
You can check the Euro level of a vehicle on its V5 registration document.
An MOT test includes a check for a diesel particulate filter. If a vehicle was fitted with a DPF when it was built, but does not have one now, the vehicle will fail the MOT.
Supplying a diesel particulate filter
It is illegal to supply DPFs that are not type-approved for use on vehicles that are Euro 5 or above.
Checking type approval
All type-approved catalytic converters and diesel particulate filters must be permanently marked by law with the following:
- an EC type approval marking
- the manufacturers name or trademark
- the make and identifying part number of the device
Figure 1 shows an example of a type approval mark for the UK.
The ‘e11’ text in the approval mark means that the part is approved for use by the UK.
Figure 1 - an example of a UK type approval mark
Not type-approved
If a part is not type-approved for the UK, it must be marked or labelled to say so.
The wording on a catalytic converter must say:
Illegal to supply for type-approved vehicles first used on or after 01/03/2001
The wording on a diesel particulate filter must say:
Illegal to supply for vehicles approved to EC Regulation 715/2007
If you are not sure whether the part you are buying is type-approved, you can ask for a copy of the type approval certificate from the manufacturer or the distributor.
Monitoring and legal enforcement
DVSA’s Market Surveillance Unit (MSU) monitors the UK market to make sure that catalytic convertors and diesel particulate filters meet legal requirements.
It does this through desk-based assessments, test purchases, and mystery shopper exercises.
If DVSA finds evidence of non-compliant replacement catalytic converters or diesel particulate filters, it can:
- prosecute the individual or business
- issue warnings
- issue recall notices
- offer advice and guidance
The Motor Vehicles (Replacement of Catalytic Converters and Pollution Control Devices) Regulations 2009 sets out the requirements for supplying and installation of replacement catalytic converters and pollution control devices.
Not following these requirements can be a criminal offence, punishable by a fine of up to £5,000.
Unsafe products
If DVSA find that a product is unsafe or does not meet the required standards, they will look to work with the relevant manufacturers to agree a plan on what they should do to fix this.
The plan will detail what you need to do to make sure your product meets safety or environmental standards. This can mean that the product will be recalled and fixed.
For information about what should happen when a vehicle recall is issued you can read vehicle safety defects and recalls: code of practice.