Abstract: A method for automated diagnosis of faults in a system containing repairable parts is performed by selecting a set of faults representing all known failures which can occur among the parts of the system, characterized by symptom data representing the expected passing or failing results for tests applied at selected test locations in the system, generating a fault/symptom matrix of the set of faults mapped to the expected passing and failing results for the selected test locations, then performing actual tests one or more test locations and correlating the actual passing or failing test results to the fault/symptom matrix in order to identify a suspect list of faults. Additional tests may be performed until the suspect list cannot be reduced further. For efficiency, the tests are selected according to which have most diagnostic significance. The design data for the parts of the system are captured and the fault/symptom matrix is preprocessed for diagnostic efficiency and speed during run time.