Model checking is very effective at finding out even subtle faults in system designs. A counterexample is usually generated by model checking algorithms when a system does not satisfy the given specification. However, a counterexample is not always helpful in explaining and isolating faults in a system when the counterexample is very long, which is usually the case for large scale systems. As such, there is a pressing need to develop fault explanation and isolation techniques. In this paper, we present a new approach for the fault explanation and isolation in discrete event systems with LTL (linear-time temporal logic) specifications. The notion of fault seed is introduced to characterize the cause of a fault. The identification of the fault seed is further reduced to a model checking problem. An algorithm is obtained for the fault seed identification. An example is provided to demonstrate the effectiveness of the approach developed.