In this paper the transistor open-circuit fault diagnostic technique that is based on the grid current prediction in the voltage oriented controlled three-phase two-level rectifier was discussed. For the current one-step prediction, the rectifier's dynamics equation was discretized using the Euler's method. The proposed technique allows to detect single and multiple transistor faults under the rectifying as well as regenerating mode of the converter in a time shorter than one current fundamental period. The technique has been validated using an experimental setup.