Data-Driven Diagnostics is a diagnostic methodology that belongs to the class of data-centric analytical approaches, distinguished by its reliance on empirical data and statistical or machine learning models—rather than explicit physical models or rule-based systems—to identify, isolate, and assess system faults or degradation states across domains such as actuator, battery, condition monitoring, diesel engine, electric vehicle, exhaust aftertreatment, flow assurance, HVAC, hybrid vehicle, and powertrain systems.