R3c01L

I am new to the forum but I had a question that can't seemed to be answered at/with a dealer or service manual.

2 Bcms' from a 2006 350z I have are sending battery voltage to the nats antenna amp of the 2006 350z via the 2 signal lines (G/W and BR). Tha manual states should be 0 volts at the nats connector, and only a slight variance when the key is turned to on, which is true if I disconnect the lines from the bcm leaving the power and ground lines connected and check the communication lines coming from the Nats ant., however 12v stays on the signal lines coming from the bcm. Question is: Is this normal?

Thanks