I finished the connection this weekend from the light panel:
When you pull down the panel, you'll see a few bundles of wires plugged in to the back end of the panel. The first plug to the left has three wires:
pink - ???
brown - ground(-)
black - +12V switched.
Assuming the wiring in the E55 aren't too different, this should work for you. But please double check with a volt meter for your car.
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I am also trying to route a remote module to the center console from the light panel. Do anyone have experience opening the cover to the A-pillar?