An implantable medical device (IMD) applies a sensor self-test when a sensing device generates a sensor signal indicating an event, or when the sensor is used to validate an event detected by another device. The event may be based on a sensed condition that triggers an operational adjustment, such as a therapy or diagnostic adjustment within the IMD. A sensor self-test verifies that an implantable sensing device is functional, and can be performed with or without activating the sensor. Activating the sensor may involve, application of an electrical input signal that causes the sensor to generate an output signal. Alternatively, the sensor self-test may be performed without activating the sensor by analyzing the continuity of a signal path between the sensor and sensor interface circuitry. In either case, a sensor self-test verifies proper operation so that operational adjustments can be made with greater confidence.