The research aim is to determine the function of the tester for running internal combustion engines of mobile agri-cultural machinery of low power. To this goal, it was proposed to run the engines of small-scale mechanization on the previously developed specialized rolling-brake tester, consisting of an asynchronous electric machine with a phase rotor connected to a three-phase electrical network and a matrix frequency. Converter included in the three-phase electrical network and consisting of nine bidirectional transistor keys, which receive signals of space-vector control from the automatic control system, associated with testing measuring equipment based on a personal com-puter. To establish the actual characteristics of the developed tester, the requirements for technical means for run-ning and of engines of small-sized agricultural machinery were formulated and trials were carried out. The experi-mental characterization was carried out in various modes, and a diesel engine F. GREENFIELD GF178 was used as a trial. The limitations of the tester in the field of setting the rotational speed for stepless and step-by-step change in the speed mode of the cold running of the engine of small-scale mechanization from 30 to 3000 rpm (with a task step of 1 rpm) with the decompressor open and from 500 to 3000 rpm (with a task step of 1 rpm) – when closed. At the same time, the deviation in the maintenance of this speed mode was in the range from 0.2 to 3.3% and de-creased with the increase in the rotation rate. Designed tester enables you to make speedy modes cold running engines small agricultural machinery power class 0.1 and 0.2 when it was created and technical service.