A focus of the paper is concerned with the issue that optimal actions of regulation, diagnostics and reliability tests of technical objects are required from the maintenance staff involved in their use and servicing, and on the other hand, that they are performed independently and autonomously in the current maintenance practice instead of being accomplished in a strictly coordinated and complex way. It was noticed that only one and common information on the object exists and provides a solid basis for coordination of the regulation, diagnostics and reliability tests. This information can be applied many times for solving various problems no matter if they concern regulation, diagnostics or reliability. Next, this paper presents an original approach of conversion of the considered information into explicit time-and-space determined “number of threshold value overshoots” of signals related to the object and its environment as well as theoretical foundations (based on various configurations of the state equation) for conversion of the considered piece of information, expressed by the aforementioned “numbers”, into the parameters of the object ability condition (i.e., its technical condition, adjustment and reliability). The theses of the presented complex method for the assessment of technical object ability were subjected to long-term verification with positive result in the study of the Allison 250 engine bearing system.