A method for coupling a control unit, in particular an engine control unit, for controlling a system, especially an engine, to a program for modeling an active chain diagnosis or to other programs for error analysis, having the following steps: within the scope of a first run, starting up an operating point of the system, generating an error and computing an intervention using a program for modeling the active chain diagnosis or the other programs for the error analysis, within the scope of a second run, resetting the control unit and deleting the error memory in the control unit, renewed starting up of the operating point, renewed applying of the error from the first run, carrying out the first intervention computed using the active chain diagnosis in the first run, and computing a second intervention using the program for modeling the active chain diagnosis, and within the scope of at least one additional run, resetting the control unit and deleting the error memory, renewed starting up the operating point, renewed application of the error, carrying out the intervention computed in preceding runs using the active chain diagnosis, and, if necessary, computing at least one additional intervention using the active chain diagnosis.