An exemplary implantable device includes a microcontroller programmed to control delivery of cardiac therapy, a connector capable of making an electrical connection to an insulated conductor associated with an exposed electrode and a circuit connected to the conductor to measure an electrical half-cell potential of the electrode via the conductor and to signal the microcontroller if a defect occurs with respect to the insulated conductor. Such a defect may be an insulation defect and/or a conductor defect. Other exemplary methods, devices, systems, etc., are also disclosed.