Inspection Check
Diesel particulate filter (DPF)
Exhaust component that traps soot from a diesel engine. Removal or visible tampering is an automatic MOT fail.
DPFs regenerate by raising exhaust temperature to burn off accumulated soot — usually on a longer run at motorway speed. Short-journey diesels can suffer incomplete regeneration and clog the filter.
Since February 2014 the MOT includes a visual check; a vehicle with the DPF removed or its core cut out and re-welded is failed immediately.