The objective of this study is to describe the methodology used to isolate the main voltage loss indicators through a simple and effective treatment of a current interrupt and current sweep. The voltage loss indicators are activation polarization, mass transport, and ohmic losses. The indicators for these losses are the Tafel slope, mass transport resistance and ohmic resistance respectively. The use of this methodology to isolate the individual voltage losses works quite well. Even though there may be some inaccuracies, the trends can be clearly seen. This methodology can be used in any PEMFC system to monitor the state of health of the fuel cell. If this method were to be automated and implemented on a periodic basis, then an on-line measurement of the individual voltage losses could be monitored. The data analysis indicates that a major objective of the controller will be to minimize the mass transport losses by implementing proper temperature control.