In this paper, we conduct a diagnosis analysis of the passenger access system, while considering a high level abstraction perspective that allows for adapting discrete event models to represent the system behavior. Firstly, we establish Petri net behavioral models for the global system functions, including the nominal operating mode and various faulty behaviors. Then, based on the established Petri net models, a diagnoser-based approach is brought into play to investigate the diagnosability of the system regarding the different predetermined classes of failures.