a method and a device for monitoring gas sensors in an internal combustion engine , in which in a steady - state operation of the internal combustion engine , the output signal of the gas sensor is filtered by a high - pass filter and higher - frequency signal components are analyzed by a comparison with an appropriately processed model value . when using the method and the device for executing the method , electrically oscillating gas sensors or the incoupling of interference variables or faults in the evaluation circuit , especially in the case of exhaust gas sensors in an exhaust - gas purification and reducing system , are able to be detected , which minimizes faulty interpretations in a dynamic diagnosis . this monitoring function is advantageously combinable with dynamic diagnosis functions that likewise analyze higher - frequency signal components by a comparison with appropriately processed model values . this increases the operational reliability of the exhaust - gas purification or reducing system .