The Failure Mode, Effect and Diagnostic Analysis (FMEDA) is a technique widely adopted by automotive industry to assess the level of reliability of hardware designs. Although very useful, it has the problem of taking a long time to complete and requires experts with extensive knowledge of the circuit under consideration. In this paper, it is presented a comparison between the analysis results obtained from an automatic tool developed by the authors with respect to the ones obtained by hand from a team of experts, followed by a critical review of the strengths and weaknesses, about the rules for automatic classification of the faults effects.