A non-intrusive and without disturbance diagnostic strategy for a low temperature Proton Exchange Membrane Fuel Cell (PEMFC) designed to operate in ŒCHP units is proposed. The developed diagnosis strategy consists of two phases: è In the first phase, an experimental campaign is conducted on a 12 cell PEMFC stack dedicated to stationary application. It is designed and marketed by Riesaer Brennstoffzellentechnik GmbH and Inhouse Engineering GmbH, Germany. Thereby, a database is built; it includes many physical signals measured from the stack and the testbench ancilliaries such as: gas pressures, flows, emperatures... and the voltage stack signal recorded with a sampling frequency of 3kHz for nominal and faulty operating conditions. è In the second phase, the research of relevant indicators for the PEMFC State-of-Helath (SoH) is made by analyzing the stamped singularities in the stack voltage signal according to the various operating conditions.