Automobile actuators have to work very reliable. In extension to redundancy schemes the use of model-based fault detection methods is advantageous for the early detection of incipient faults in the process or in the signals. Two different approaches, the parity-space method and the parameter estimation approach, are selected for the investigations for the example of an automobile actuator driven by a d.c. motor. After a brief description of the theoretical basis the experimental application follows to several faults.