To obtain a secured mating of electric connectors is one of the most important steps in a robotic wiring harness assembly system. Although there are plentiful results about complex peg-in-hole assembly problems, little work has been done with respect to this special issue. In many cases, mating connectors can be regarded as a hole search process of a multiple hole-in-peg problem. Because various faults might occur during the search, a reliable error recovery strategy is necessary in the mating task. In this paper, we model possible faults as "trap regions" in the configure space (C-space) of the assembly. Fault isolation methods are obtained from elaborated force analyses as well. Based on these fault isolation results, error recovery strategies are proposed according to the fault models. A fault-tolerant mating of electric connectors can then be achieved. The effectiveness of the methods is finally confirmed by experiments.