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 (CRT) and updating a result counter (FCRT). Validation is performed depending on test result once the event counter has reached a first maximal value (CTRmax) or once the realization counter has reached a second maximal value (FCTRmax). 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.