Reliability and durability are key considerations to successfully deploy Proton Exchange Mem-brane Fuel Cells (PEMFCs). Defects can appear on different membrane electrode assembly (MEA) components and under different forms due to manufacturing processes or operational aging of the fuel cell and may propagate in the stack. Defects-propagation in PEMFC stack is investigated considering a FCDLC cycle. The stack consists of 35 cells with 5 cells including a defect (cell number 11-15). The latter MEAs are custom-ized with lack of anode catalyst layer for 25% of the total surface area at one location close to the hydrogen outlet. The PEMFC was operated during 561 hours. The MEA with default aged faster than the one without any default. Nevertheless, the cells 9,10 and 16 close to the default age also faster indicating a propagation effect. The defect-propagation is investigated thanks to magnetic field on the three sensor arrays [1]. Indeed, the inversion of this signature of the magnetic field measurement allows the reconstruction of a heterogeneous current with lowered current densities on the default zone of the cells.