Abstract: The invention relates to a diagnostic method for checking the functionality of a component for the exhaust-gas aftertreatment of an internal combustion engine. For this purpose, in an internal combustion engine, a secondary air supply is provided by means of which an excess of oxygen can be generated in the exhaust gas channel essentially independently of the operating conditions of the internal combustion engine, and wherein said excess of oxygen is utilized for the measurement of an oxygen storage capacity of the component or of a signal change at the component. It is provided that the component is subsequently subjected to a substoichiometric exhaust gas in order that the oxygen release capacity or the signal change upon a change from superstoichiometric exhaust gas to a substoichiometric exhaust gas is also taken into consideration in the diagnosis. The invention also relates to a device for exhaust-gas aftertreatment, which is designed to be able to carry out a method of said type.

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: An exhaust system of a multi-cylinder internal combustion engine includes at least one first gas sensor, which is sensitive for at least one component of the exhaust gas and is arranged in the exhaust system, for determining an air/fuel ratio supplied to the internal combustion engine. It also includes a regulating device for regulating the air/fuel ratio as a function of a signal supplied by the gas sensor and at least one first catalytic converter arranged in the exhaust system. At least one first catalytic converter is arranged in a position of the exhaust system close to the internal combustion engine so that it is upstream from the at least one first gas sensor in the direction of flow of an exhaust gas of the internal combustion engine, and the regulation device includes a regulator which receives the signal of the first gas sensor as input, and in which an algorithm for cylinder-selective determination and regulation of the air/fuel ratio is stored.

Abstract: An exhaust system of a multi-cylinder internal combustion engine includes at least one first gas sensor, which is sensitive for at least one component of the exhaust gas and is arranged in the exhaust system, for determining an air/fuel ratio supplied to the internal combustion engine. It also includes a regulating device for regulating the air/fuel ratio as a function of a signal supplied by the gas sensor and at least one first catalytic converter arranged in the exhaust system. At least one first catalytic converter is arranged in a position of the exhaust system close to the internal combustion engine so that it is upstream from the at least one first gas sensor in the direction of flow of an exhaust gas of the internal combustion engine, and the regulation device includes a regulator which receives the signal of the first gas sensor as input, and in which an algorithm for cylinder-selective determination and regulation of the air/fuel ratio is stored.