Shop 2552 catalytic converter from 17 trusted brands including WALKER, BOSAL, EEC. Compare prices, check vehicle compatibility, and get free delivery on orders over £99.
The catalytic converter — commonly called the cat, cat converter, or exhaust catalyst — is an exhaust after-treatment device containing a ceramic or metallic substrate coated with platinum, palladium, and rhodium. These precious metals catalyse the chemical conversion of harmful carbon monoxide, unburned hydrocarbons, and nitrogen oxides into carbon dioxide, water, and nitrogen. A failed cat causes an MOT failure on exhaust emissions, triggers lambda sensor fault codes, and can severely restrict exhaust flow if the substrate has collapsed. CarParts247 stocks direct-fit replacement catalytic converters from BM Catalysts, Bosal, Walker, and Klarius for a wide range of petrol and diesel vehicles.
A deteriorating cat gives several warning signs before it fails completely. Recognising them early prevents the cost of a new oxygen sensor or even engine damage from a collapsed substrate blocking the exhaust.
Thermal damage is the leading cause. Misfires send unburned fuel into the exhaust, where it ignites inside the cat and melts the ceramic substrate. Oil burning and coolant leaks contaminate and poison the precious metal coating, destroying its catalytic activity.
OEM catalysts from manufacturers such as BM Catalysts and Klarius carry Type Approval certification for UK and EU use, ensuring they meet the emissions standard applicable to the vehicle's registration date. Budget or non-Type-Approved units may fail the MOT's visual inspection if a EURO 5/6 vehicle is fitted with a converter lacking the correct approval markings.
Commonly searched OE numbers fitting Catalytic Converter from the TecDoc catalogue.