Diagnostics versus prognostics

Published 15 January 2020



Murray Wiseman
Global Facilitator & Consultant
Living RCM Practitioner

Where is the divide between the process of troubleshooting and that of predictive condition-based maintenance? Both sets of procedures require condition data and knowledge of failure behavior. How do these distinct processes work with one another? Some confusion in the purchase and application of maintenance technology tools can arise when the particular problem lacks sufficient definition for matching it up with the required technological solution.


Something is wrong. The situation merits time and effort by a technician to troubleshoot the system and find the cause of the alert indicator. In this case, he needs the shortest path to a solution provided by reasoning systems such as SpotLight.

Predictive Maintenance

Nothing wrong yet. However some internal part or component is degrading. (In RCM this is called a “Potential Failure”.) Or, some part has incurred accumulated stress to the point that it’s resistance to failure has diminished. In either case, if something is not done a “Functional Failure” will occur. Once the Predictive Maintenance decision is made to intervene, the diagnostic process kicks in. Troubleshooting a potential failure (i.e, not yet a functional failure) requires that you are aware of the leading symptoms that are precursors to a functional failure.