Abstract: A process for detecting a state of a catalyst system installed in an exhaust gas channel of an internal combustion engine of a motor vehicle, through which catalyst system exhaust gas from the internal combustion engine flows so that the exhaust gas can be purified, the process including the steps of: detecting at least one operating parameter of the catalyst system over a predetermined time period, determining a total energy output of the internal combustion engine within the predetermined time period, and calculating a characteristic value (k) based on a ratio of the at least one operating parameter to the total energy output.

Abstract: The invention relates to a method for improved monitoring of the conversion rate of an exhaust gas catalytic converter for an internal combustion engine. To achieve this, the temperature values determined downstream from the exhaust gas catalytic converter within a given time window is added with time interval (dt). A starting time (tA) and a time interval (dt) are influenced inter alia according to the operating mode of the internal combustion engine by taking into account fuel mass flow during a given time period. The total value arising during time interval (dt) below a curve (25) is compared with a limiting value and an error signal is outputted once a given deviation value is reached.

Abstract: To improve monitoring of the conversion rate of an exhaust catalyst for an internal combustion engine, the HC emissions are determined downstream of the exhaust catalyst during a predetermined time interval. The time interval starting point and the time interval duration are dependent on the operating mode of the internal combustion engine which is detected, for example, by consideration of the fuel mass flow to the engine over time. The HC sum value thus accumulated during the time interval is compared with a limit value and, when a predetermined difference value results, an error signal is generated.