A method for monitoring operation of a variable geometry turbocharger device includes monitoring exhaust gas pressure and vane position of the variable geometry turbocharger device. Exhaust pressure and vane position are estimated. Residual exhaust pressure and vane position are calculated based upon differences between the estimated and monitored exhaust gas pressures and vane positions. The turbocharger is determined operating properly based upon the exhaust pressure residual and the vane position residual.