The aim of this study was to highlight the interest of using CFD technique as a diagnostic tool of a malfunctioning Solid Oxide Fuel Cells. Hydrogen starvation of a SOFC due to nitrogen dilution is one of the cell dysfunctions and can lead to its degradation. Identification of the starvation point allows to improve cell performance and establish the best conditions for degradation tests. To illustrate a potential of the CFD tool, several simulations of a single planar SOFC and its behaviour under hydrogen starvation were performed and analysed. The results showed that at lower cell voltage values of 0.3 and 0.5 V significant gradients in the electric current were noticed due to a local reduction in hydrogen concentration. The CFD analysis allowed defining desirable mass flow rate of hydrogen to SOFCs to avoid fuel starvation. The model constitutes a helpful tool for optimizing cell design and operational conditions.