An implantable medical device capable of sensing cardiac signals and delivering cardiac electrical stimulation therapies is enabled to detect a short circuit of a medical electrical lead. A physiological signal correlated to a motion of a patient is sensed via a physiological sensor. If a lead monitoring condition is met based on the physiological signal, a cardiac signal is acquired and analyzed to detect an abnormality. The short circuit of the medical electrical lead is detected in response to detecting the abnormality.
