Systems and methods are provided for a diagnostic system for a machine with a combustion engine and a variable geometry turbocharger that includes a vane position sensor. The diagnostic system includes a controller configured to calculate a learned span value of the turbocharger based on the output of the vane position sensor during a diagnostic procedure and a reference vane position sensor value. A plurality of learned span values are calculated each during a different one of a plurality of diagnostic procedures performed over a period of time and a first regression analysis to predict an expected learned span value at a defined future time using the calculated learned span value and the plurality of stored learned span values. An alert message is generated when the expected learned span value is indicative of a potential future fault of the turbocharger.