Originally Posted by Qsilver7

Is this for an e53 or e70 X5? If e53...some of the features like highbeam and lane departure probably won't work since the e70 uses a totally different communication bus.

But for an e53...you can add mirror with HOMELINK buttons or auto dimming because they only require 12volt power and are independently contained in the mirror. Those features don't communicate with a control module somewhere else in the com-bus.

If you have an e70...again the HOMELINK and auto dim is located in the mirror, so only 12 volts needed to operate...which should be already in wiring harness. The side mirrors though...will not dim if they aren't EC and connected to the interior mirror through the wiring harness running to the door (or however the e70 sends data over its com-bus).

If you have an e70...then some of the options mentioned in this thread like lane departure and highbeam assist may require more since it involves communication with other components outside the mirror or components located on the windshield (rain & light sensors).