In a PEMFC with Pt anode under CO poisoning, the possibility and conditions for the occurrence of autonomous potential oscillations in galvanostatic operation were investigated. A special experimental setup consisting of a differential H-2/H-2 cell was used, in order to eliminate the masking effect of the cathode and to avoid spatial distributions along the channel. The influence of CO concentration and temperature on the behaviour of the oscillations was analysed. A model developed for cells with PtRu catalyst was adapted to fit the experimental data. The comparison of the original and adapted parameter set revealed lower water dissociation and CO oxidation constants at Pt. (C) 2011 Elsevier Ltd. All rights reserved.