A method for controlling a filling of an exhaust gas component storage device of a catalytic converter in the exhaust gas of an internal combustion engine, the method comprising:
- ascertaining an actual fill level of the exhaust gas component storage device using a first system model, to which signals of a first exhaust gas probe that extends into the exhaust gas stream upstream from the catalytic converter and acquires a concentration of the exhaust gas component are supplied when this first exhaust gas probe is ready for operation;
- specifying a lambda target value for a first control loop by a lambda target value pilot control;
- supplying, when the first exhaust gas probe is not ready for operation, a replacement signal for the signal of the first exhaust gas probe to the system model;
- and
- using the replacement signal in the lambda target value pilot control as an initial value for the lambda target value.