This paper proposes an innovative fault-diagnosis system for a turbocharged diesel engine with variable-geometry turbocharger control. Numerous and diversified actuator and/or sensors faults are identified and analyzed such as air-leakage in the admission collector, compressor malfunctioning, intake-valves fault, intercooler fault, deterioration in the turbine-compressor coupling, defect in the variable geometry of the turbine and fault in rotational speed sensor. Furthermore, a complete non-linear engine model with four state variables is adopted. The proposed strategy consists in developing a Fault Detection and Isolation algorithm (FDI) based on the theory of Gain Schedule Control operated on a Takagi-Sugeno model of the diesel. Simulations with a nonlinear Diesel model in the presence of noise were carried out and which demonstrated the effectiveness of the proposed algorithm. Moreover, the robustness properties of the used H-infinity FDI filters exhibited significant rejection of disturbances and noise-effects attenuation which make the proposed strategy adequately close to the conditions of the real physical system.