Check the wiring near the right side hinge of the upper tailgate. There is a yellow/white_striped wire that goes from the antenna amp to the GM5 module. The wire was broken inside the rubber boot in my X.

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ex X5 4.4 -01 (build 10/00) diamantschwarz metallic

ex 316i -03 Saloon Japan red
ex 316i -90 (two door) hennarot
ex 528iA Tour -97 biaritzblau metallic
ex 318iS Coupe -92 kaschmirbeige metallic
ex 316i -92 vulkangrau