A method and apparatus for detecting and analyzing errors in a communications system is described. The method employs expert system techniques to isolate failures to specific field replaceable units and attempts to restore the failing unit to service, if the system will not be adversely affected, by removing it from service, resetting the resource and returning it to service if it passes retesting. The expert system techniques include detailed decision trees designed for each resource in the system. The decision trees also filter extraneous sources of errors from affecting the error analysis results.