We propose a simple & practical probabilistic model, using multiple incomplete test concepts, for fault location in distributed systems using a Bayes analysis pro- Since it is easier to compare test results among processing units, our model is comparison-based. This approach is realistic & complete in the sense that it does not assume conditions such as permanently faulty units, complete tests, and perfect or nonmalicious environments. It can handle, without any overhead, fault-free systems so that the test procedure can be used to monitor a functioning system. Given a system S with a specific test graph the corresponding conditional distribution between the comparison test results (syndrome) and the fault patterns of S can be generated. To avoid the complex global Bayes estimation process, we develop a simple bitwise Bayes algorithm for fault location of S, which locates system failures with linear complexity, making it suitable for hard real-time systems. Hence our approach is appealing both from the practical & theoretical points of view.