Method of judgement of the quality of the exhaust catalyst in the exhaust path of an internal combustion engine of a vehicle

The method involves detecting the actual catalysing temperature in dependence on reaching a predetermined oxygen storage capacity value of the oxygen reservoir. This temperature is compared with a comparison value related to the same oxygen storage capacity value and then determining the temperature rise if a higher actual temperature is determined . The light-off temperature is then determined as a value proportional to the temperature rise, preferably a linearly proportional value. the catalysing temperature comparison value is recorded in a characteristic field of an engine management system. Independent claim describes engine management system for carrying out this method.