Here is the wiring diagram. The actuator gears are plastic...stock. Therefore, I wouldn't be applying voltage at a whim because you can easily strip them--and it's sorta a pain in the butt to replace it because of the heatshield n stuff.

On normal operation, the xcase is only in use under speeds of about 25mph-ish and then in some slip instances. Other than that, it is "off" in normal driving conditions. There is a strategy to help prevent over/under-steer conditions, and I've noticed this myself when going around a sharp corner and hitting the road-"turtles" causing a wheel to slightly slip. Other than that, I wouldn't recommend driving around with the xcase in fully engaged AWD. Also, this will completely wear out the clutches as they will be sacrificed. These xcases are north of $1500 rebuilt.

At usual key-on/off events, the vehicle determines where the end points are on the xcase. I think this is done with calculation of the current draw in correspondence of the actuator.

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Calibration sequence:
When terminal 15 is OFF, a calibration sequence is performed. During this calibration sequence, a certain angle setting of the VTG actuator motor has a corresponding locking torque assigned. The effects of wear are also taken into account when this is done.

The multi-plate clutch is closed fully and separated once during this calibration sequence. When this happens, the current draw is measured at the respective angle setting of the VTG actuator motor. This determines the beginning and end of the closing movement for the multi-plate clutch. The angle setting is recorded by means of the integral incremental sensor in the VTG actuator motor. These values are stored and are used as data when the car restarts.
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2003 BMW X5 3.0i -- MT5, 3.64s final gears, H&R lowering springs, K-Mac bushing kit
2007 BMW X3 3.0Si -- MT6