The invention involves monitoring on a continuous or non-continuous basis the electrical drain of a chronically implanted physiologic sensor. One of a pair of conductors is monitored for excessive current drain. For example, if an inner sensor-signal bearing conductor (of a co-axial pair) contacts conductive body fluid or tissue (e.g., due to insulation breach), a measurement of current quickly reveals the fault. Accordingly, if an increase in or a supra-threshold electrical current drain is detected the sensor power supply is disengaged. In one form, dedicated physiologic sensor to electrical circuitry disposed within the AIMD. In another form, the AIMD is adapted to sense a physiologic parameter and deliver therapy (e.g., via one or more electrodes). A manual or automatic reset can be implemented in the event that the failure mode resolves itself. The reset can include criteria such as three consecutive sub-threshold current measurements before normal operation resumes.