I’m being located :O

Dear readers, I have registered here from the plight, in the hope that you can help me further. I am constantly located (without my consent) over my car and that is from my ex. I have now brought my car to the Porsche plant 2 months ago for search, but the result was sobering. They did not find a tracker in or under my car! I have (when I noticed that the tracking continues) the car a second time in a workshop I mean, if there’s a tracking device on the car, would it have been noticeable?! Also in the car (glove compartment etc.) we searched everything. Now my question, it is possible for him via my navigation system (drive the Porsche Cayenne Turbo BJ 2012, Navi therefore at the latest) or any other program, to determine my location or even there are tracking transmitters with long-term battery, which can be used with the best will as a la he doesn’t find it? I would be very grateful if you would pass on your experiences or knowledge in this regard to me, hardly know myself and would hate to entrust myself to good acquaintances because I find the whole thing a little “sick”. With very dear greeting, Assal