A fault isolation and ambiguity resolution system comprising: one or more analytic engines executable by a processing system, the one or more analytic engines configured to detect a fault associated with a monitored system based on data extracted from one or more data repository; and a reasoning system comprising: a single fault isolator configured to identify an ambiguity group including the fault and one or more related faults of the monitored system; and an inference system configured to utilize evidence to resolve ambiguity between the fault and the one or more related faults of the ambiguity group as a diagnosis result; characterised in that the reasoning system is configured to: perform an ambiguity group ranking and determine an associated confidence; select the ambiguity group having a first rank; identify a plurality of fault modes in the ambiguity group having the first rank; locate support evidences based on a diagnosis matrix for the identified plurality of fault modes; invoke the one or more analytic engines to produce evidence values based on accessing the one or more data repository for each of the located support evidences; determine an evidence belief confidence for each of the located support evidences; aggregate the evidence belief confidence for each fault mode; and determine a fault mode with the highest evidence belief confidence as the ambiguity resolution. one or more analytic engines executable by a processing system, the one or more analytic engines configured to detect a fault associated with a monitored system based on data extracted from one or more data repository; and a reasoning system comprising: a single fault isolator configured to identify an ambiguity group including the fault and one or more related faults of the monitored system; and an inference system configured to utilize evidence to resolve ambiguity between the fault and the one or more related faults of the ambiguity group as a diagnosis result; a single fault isolator configured to identify an ambiguity group including the fault and one or more related faults of the monitored system; and an inference system configured to utilize evidence to resolve ambiguity between the fault and the one or more related faults of the ambiguity group as a diagnosis result; characterised in that the reasoning system is configured to: perform an ambiguity group ranking and determine an associated confidence; select the ambiguity group having a first rank; identify a plurality of fault modes in the ambiguity group having the first rank; locate support evidences based on a diagnosis matrix for the identified plurality of fault modes; invoke the one or more analytic engines to produce evidence values based on accessing the one or more data repository for each of the located support evidences; determine an evidence belief confidence for each of the located support evidences; aggregate the evidence belief confidence for each fault mode; and perform an ambiguity group ranking and determine an associated confidence; select the ambiguity group having a first rank; identify a plurality of fault modes in the ambiguity group having the first rank; locate support evidences based on a diagnosis matrix for the identified plurality of fault modes; invoke the one or more analytic engines to produce evidence values based on accessing the one or more data repository for each of the located support evidences; determine an evidence belief confidence for each of the located support evidences; aggregate the evidence belief confidence for each fault mode; and determine a fault mode with the highest evidence belief confidence as the ambiguity resolution.