The present application relates to a method for determining multiple simultaneous fault conditions on complex systems. The method comprises receiving symptoms of a complex system from monitors. When some of the symptoms suggest the existence of multiple simultaneous fault conditions, then the method creates a symptom signature, creates one or more failure mode signatures, and creates an error code for each failure mode signature in regard to the symptom signature. Each failure mode signature is associated with only one failure mode. A Hamming distance is determined for each failure mode indicated as possibly causing the original fault condition. Each failure mode with the minimum Hamming distance and same Hamming Code are grouped together as being one of the multiple simultaneous fault conditions. All remaining failure modes with other Hamming distances are then assigned into one of the simultaneous fault conditions.