An implantable medical device capable of sensing cardiac signals and delivering cardiac electrical stimulation therapies is enabled to detect a short circuit condition. In one embodiment, a cardiac signal is sensed by a sensing module coupled to electrodes. A controller identifies signal events in response to the cardiac signal and detects a short circuit condition in response to at least one of the signal events having an amplitude crossing a short circuit detection threshold and a maximum of two signal events crossing the short circuit detection threshold occurring between two adjacent events having amplitudes not crossing the short circuit detection threshold. In one embodiment, the signal events are identified from a differential signal determined from the sensed cardiac signal.
