The MKIV has two lever type plugs on the left rear of the unit (blue and burgundy colored). It has one small black shielded wire plug on the right rear of the unit. It is the GPS antenna cable and the plug pulls straight off. Follow it to the antenna puck which is about1.5 inches square IIRC. It is in the front on Z4s but I think it is in the rear on X cars. It is not a part of the shark fin. My info mostly relates to the e38/39/46/53 I-bus cars.

It seems that the Z4 and X3 are different in the type monitor and monitor controls. The Z4 has the GPS antenna up in the dash area and maybe the X3 does also. The P/N is 65 90 0 010 509. I assume that the MKIV unit is the same for all of these cars though. So I would think the GPS antenna would have to have a cable going to the nav computer even if the antenna itself is in the dash.

Look here. http://www.penskeparts.com/DiagramsB...ts=65900010509