Real-time systems interact with their environment, through time constrained input/output events. The misbehavior of real-time systems is generally caused by the violation of the specified time constraints. Validation of real-time system software is an important quality control activity in the software lifecycle. Among the validation processes, testing aims at assessing the conformance of an implementation against the reference specification. One of the important aspects in testing real-time software systems is the fault coverage measurement, which consists of studying the potential faults that can be detected by a test suite generated by a given test generation method. This paper addresses the fault coverage of the Timed Wp-method we have introduced in [EDKE98]. We present a timed fault model based on the TIOA model for real-time systems specification. We study the fault coverage of the timed Wp-method with respect to our fault model.