We propose a unified approach for diagnosis of defects of different types. We use a new fault model called pattern-dependent stuck-at faults to narrow down the list of candidate defect sites. The important property of pattern-dependent stuck-at faults is that they encompass the behavior of other fault models. By using a specific subset of the pattern-dependent stuck-at faults to perform an initial diagnosis, we can accurately and efficiently identify a list of candidate defect sites independent of the defect type. We present experimental results of diagnosis of transition faults and of bridging faults as examples to demonstrate the proposed approach and its ability to diagnose faults of different types.