The use of piezoelectric wafer active sensors in structural health monitoring systems implies the necessity to check these components for their functionality, especially when the sensors are embedded in the structure. This paper introduces two novel approaches based on electro-mechanical impedance measurements and compares them with a traditional approach based on the slope of the susceptance spectrum. The change of the resistance spectrum as well as the change of the correlation of susceptance spectra is established as damage indicator. In an experimental setup the mechanical durability of a piezoelectric patch transducer, directly embedded in the structure, was tested. It has been shown that this application of load causes partial sensor breakage, which, for this particular type of PWAS, can hardly be detected with the help of the susceptance slope. The good feasibility especially of the proposed damage indicator, based on correlation within the susceptance spectrum, is demonstrated.