Removing emissions equipment is not the same as repairing a fault or selecting a suitable replacement. This guide replaces earlier removal and delete advice with the relevant UK inspection guidance.
Missing or modified equipment
Department for Transport guidance states that a missing DPF, where one was fitted when the vehicle was built, results in an MOT failure. It also explains that removing a DPF will almost invariably breach the road-use emissions requirements it describes.
The current MOT manual includes checks for manufacturer-fitted emissions equipment. Missing, obviously modified or obviously defective equipment can be a major defect under the applicable inspection rules. The exact checks depend on the vehicle and the manual’s applicability provisions.
Check approval and zone requirements separately
Ask for the replacement part’s required type approval and confirmed application. The DVSA guide to supplying and fitting catalysts and DPFs explains the applicable approval rules. For London charging-zone questions, use TfL’s official ULEZ vehicle checker and its enquiry process. CATman’s parts finder does not certify ULEZ status or establish that a replacement changes a vehicle’s emissions class.
What to do when there is a fault
Have the cause diagnosed, establish the required repair and identify the correct component. Do not treat a smoke-test result alone as evidence that a modified vehicle complies with every applicable requirement.
Request a suitable replacement
Send the registration, engine, part reference and relevant specification to CATman. Confirm the final application with the supplier and fitting garage. This page does not offer removal, bypass, ECU-delete or tuning instructions.
Sources: Department for Transport DPF guidance and the current DVSA MOT inspection manual. Check the official guidance for the rules applicable to your vehicle.