A current disadvantage of IDDq testing is lack of software-based diagnostic tools that enable IC vendors to create a large database of defects uniquely detected with this test method. We present a methodology for performing defect localization based upon IDDq test information (only). Using this technique, fault localization can be completed within minutes (e.g. <5 minutes) after IC testing is complete. This technique supports multiple fault models and has been successfully applied to a large number of samples-including ones that have been verified through failure analysis. Data is presented related to key issues such as diagnostic resolution, hardware-to-fault model correlation, diagnostic current thresholds, and the diagnosability of various defect types.