a process for validating the fault detection of a device under test includes carrying out a series of basic tests of the device under test . each basic test leads to a positive or negative result indicating normal or abnormal functioning of the device under test . the process also includes , after each realization of a basic test , updating an event counter and updating a result counter . validation is performed depending on test result once the event counter has reached a first maximal value or once the realization counter has reached a second maximal value . the process can be performed by a diagnostic device . the process and device can monitor the electric or functional performance of more or less complex systems installed in an automobile .