Fault diagnosis is to predict the potential fault sites in a logic IC. In this paper, we particularly address the problem of diagnosing faults that exhibit the so-called Byzantine General's phenomenon, in which a fault manifests itself as a non-logical voltage level at the fault site. Previously, explicit enumeration was suggested to deal with such a problem. However, it is often too time-consuming because the CPU time is exponentially proportional to fanout degree of the circuit under diagnosis. To speed up this process, we present an implicit enumeration technique using symbolic simulation. Experimental results show that the CPU time an be improved by several orders of magnitude for ISCAS85 benchmark ciruits.