Abstract: This paper presents an approach to construct a fault message matrix based on the functional block diagram and signal flow chart of the system or equipment. By analyzing the contribution of the test points to fault detection and fault so lation, the matrix is resolved step by step , the most necessary test points are identified and optimal diagno stic procedure is determined. Thus, the purpose of fault detection and fault iso lation is reached by the use of the fewest test　points and a short - time test.

Key words: checkout, malfunction, detection, iso lation