If you want to use carX then you should connect it to the tape or cd in your case, there is no way for you to control pc from you car if you use AV channel.
Read full carx instructions and you will understand how and why

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X5 4,4i-06 Current
330Ci Cab-03 2007-2008
MB E55 AMG-03 2006-2007
Z3 2,8 Roadster-98 2006-2007
X3 2,0d-05 2005-2006
320d-99 1999-2005