Abstract: A method of identifying faulty units in a computer-controlled system. The system units generate error reports in response to the detection of error conditions. When an error report is received, an initial list is generated containing probable fault weights for each of the system units based on the type of the error report. The probable fault weights are prespecified based on a logical analysis of the fault modes and error propagation paths in the system. A history list of fault weights is first aged and then combined with the initial list to generate a resultant list. The resultant list becomes the new history list. The resultant list is then masked by the initial list to form a selection list from which a most probable fault unit is selected.