Abstract In this paper, DACS stands for Defects that Affect Chain and System, which could be any type of silicon defects caused by an unintentional interaction between a scan chain signal and a system logic signal. The device could fail scan chain testing or show up as a latent failure in the customer’s system. A novel diagnosis methodology is proposed to locate both ends of a DACS. The proposed algorithm can be generally applied to any type of DACS. Experimental results on industrial chips demonstrate the effectiveness of the proposed method.