As various faults alter the PEM fuel cell impedance characteristic over a broad frequency range, the electrochemical impedance spectroscopy is frequently employed for the purpose of condition monitoring. The proposed methodology treats the impedance components among different frequencies as dependent complex random variables. The information about fuel cell condition is incorporated into the dependence structure of these complex random variables. This dependence is described through the corresponding joint cumulative density function by employing copula functions. The benefits of such an approach are threefold: (i) the estimation of the joint cumulative density function requires only several measurements of a fuel cell in a fault-free condition, (ii) the procedure is computationally efficient, and (iii) the output of the copula function is directly used as an overall unit-free condition indicator. The approach was evaluated on a kW-range PEM fuel cell stack subjected to water management faults of various seventies. The results show that the ci corresponds with the severity of the induced faults. (C) 2015 Elsevier B.V. All rights reserved.