In this paper, we focus on two notions of diagnosability for labeled Time Petri net (PN) systems: K-diagnosability implies that any fault occurrence can be detected after at most K observations, while r-diagnosability implies that any fault occurrence can be detected after at most r time units. A procedure to analyze such properties is provided. The proposed approach uses the Modified State Class Graph, a graph the authors recently introduced for the marking estimation of labeled Time PN systems, which provides an exhaustive description of the system behavior. A preliminary diagnosabilty analysis of the underlying logic system based on classical approaches taken from the literature is required. Then, the solution of some linear programming ...