An implantable medical device system includes an implantable device and an external locator device for percutaneously locating detecting port opening of the implantable device. The implantable device includes a port chamber forming the port opening, a septum sealing the port chamber relative to an exterior of the device, and a coil positioned at a known location relative to the port opening. The locator device includes a controller, at least one X-loop electrically coupled to the controller and oriented along a first major axis, and at least one Y-loop electrically coupled to the controller and oriented along a second major axis differing from the first major axis. The system is configured such that when the locator is spatially proximate the coil, an induced voltage in at least the Y-loop(s) is read by the controller to indicate a location of the coil relative to the locator device.