At present, in order to automate and informative processes in distribution zones (DZ) with a voltage of 0.4 kV, new technologies have found wide application in the form of automated meter reading and control system (AMRCS). However, as part of these information systems, there are no technologies focused on solving diagnostic problems. The report proposes methodological and algorithmic foundations for constructing a subsystem for diagnosing the states of wires of the main lines of DZ. Diagnostic criteria are formulated based on the assessment of the level of their run-out. The research results are aimed at improving the existing AMRCS and increasing the reliability of distribution networks.