The invention concerns a procedure and a device for an adaptation of a dynamic model of an exhaust gas probe, which is a component of an exhaust pipe of a combustion engine and with which a lambda value is determined for regulating an air-fuel composition, whereby a simulated lambda value is calculated parallel to that in a control unit or in a diagnosing unit of the combustion engine and an application function uses the simulated and the measured lambda value. According to the invention it is thereby provided that a jump behavior of the exhaust gas probe is determined during a running vehicle operation by evaluating a signal change at a stimulation of the system and that the dynamic model of the exhaust gas probe is adapted with the aid of these results.