This paper presents an automated method for fault diagnostics in the mechatronic modules of the optical-location stations. Apart from the existing methods, the use of an object native control system for the diagnostics purpose is discussed. It allows us not to use an external hardware during the diagnosis process, because all the information concerning the state of a mechanical structure could be acquired from the control loop information (data from the feedback sensors, outputs of the equalized filters, etc.). This data is enough to detect even the smallest mechanical defects. In future automatization of the control loop data analysis will allow even a low-qualified staff to diagnose and eliminate complex failures, critical for the precise mechatronic modules during the serial production. This is extremely important, because even small mechanical defects can influence the tracking precision of a complete system. This method was successfully implemented for the serially produced modules for the optical-location stations. Realization of the described method requires construction of an adequate mathematical model of a mechatronic module. The authors describe development of an ideal system model, including a servo-drive, a control system and additional hardware, such as sensors and servo-controller parameters. A list of typical failures for these types of systems is presented. This list was obtained after experimental diagnostics of over 100 produced units. The authors also describe how these failures can be presented in a mathematical model. An experiment is required to prove the effectiveness of this method by comparison of the model data with the data acquired.