This paper resolves two issues regarding diagnosis of tunneling opens: efficient screening and accurate localization. In the first part, a test pattern selection and sorting algorithm is presented. It is shown that the presented algorithm savesIDDQ (t) test time without impacting on its effectiveness. The second part of this paper presents a locating algorithm which combines both VLV and IDDQ (t) test results. This technique is shown to be able to accurately locate the tunneling opens with higher resolution than a commercial single stuck-at fault diagnosis tool.