The article presents the historical materials about the creation and growth of GOSNITI, its employees who developed and implemented methods and means of diagnosis, maintenance and repair of machinery and tractor fleet of the agro-industrial complex of the country. The information on the history of the mathematical apparatus to the method of reli-ability control machines to minimize the total unit costs of maintenance and repair, taking into account the costs of downtime of faulty machines are presented. (Research purpose) The approbation of the express method of substantiation for diagnostic and structural pa-rameters of machine elements and analysis of the results of the development, production and implementation of MTP diagnostic tools in the agricultural sector of the USSR. (Materials and methods) We have analyzed the achievements of the GOSNITI teams, other research institutes and universities of the country, the engineering service of agriculture, statistical data on the production and use of diagnostic tools for tractors and cars. (Results and dis-cussion) The article reviews universal approach by V. M. Mikhlin of feasibility study of permissible values of resource and diagnostic parameters. The article notes that the Finnish mathematicians implemented it in the universal computer program TURBO-NEK, which al-lows optimizing the permissible values of diagnostic and structural parameters of machine elements, other characteristics in the organization of technical operation of machines. We have tested the express method of calculation of permissible values of structural and diag-nostic parameters taking into account the real rates of change in the values of parameters in operation. We have described the engineering and calculation method of limiting and per-missible parameters of diesel engines, their parts and interfaces in the guidance technical material of 10.16.0001.008-89 as a result of thirty-five years of work of the repair laborato-ry of GOSNITI. We have considered the results of the creation and implementation of diag-nostic equipment, aspects of scientific, technical and organizational difficulties in its devel-opment, production, movement and use. (Conclusion) We have prepared proposals for the resuscitation of diagnostics of the machine and tractor fleet of the agro-industrial complex for the coming period. In addition to the parameters measured by built-in and external means of control, it was proposed to legalize the equal use of organoleptic control of the state of machines, for which a wealth of experience has been accumulated.