This statement is actually opposite. The TV and nav modules are in a master/slave configuration. However, when both are present, it is the navigation that overrides TV. I have both, and I have tried it. The nav runs the screen whenever it is connected. The TV only runs the screen when it is the sole component connected.

Now, the video signals pass through the TV module when both are connected, but it is just a pass through. The actual signals come from the nav computer. And, the TV module just stays idle until told by the nav computer to turn on and steal the signal path.

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SOLD
2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input