Catalytic converters are now fitted to all cars to remove harmful emissions from the exhaust gases.

Although they often look like a normal exhaust silencer they are in fact a high tech device with ceramic cores and expensive catalysers incorporating platinum or palladium.

The catalytic converter will also normally have attached to it the Lambda sensor which measures the percentage of Oxygen in the exhaust gas and transmits information to the vehicles engine management system.

If the catalytic converter or Lambda sensor are not working correctly it is likely that the car will fail its MOT test due to an excess of harmful exhaust emissions. The car will also run poorly as the engine management system attempts to correct false information from the sensor.

Although catalytic converters are designed to have a long life expectancy
and will not rust, they can be damaged if the engine is not properly
tuned and excess fuel or oils run through them. Due to their
delicate ceramic insert they can also be damaged by sudden
jolts such as vehicle impact or bump starting the car.