The sensor on the front of the autodim mirror is to disable the mirror dimming feature during daylight. The sensor for the automatic headlights is integrated with the rain sensor.
Yes, there is a "reinitialization" procedure that can be done to clear the learning memory of the rain sensor. I may try that if everything else fails, since I have to take it to the dealer for that. From what I understand, it's only rare cases where that needs to be done (and actually solves anything).
My next task is to swap the sensors (just the sensors, not the glued-on lenses) between my two cars, to see if that changes anything. If not, I'll go to the dealer for the reinitialization.
2003 325xi BlackČ