I have had my 2005 X5 (45k miles) california car for a few months now, and frankly, with variety of sensors that have gone crazy on it so far, I have almost lost all confidence in anything electrical on this car. That is why I was worried a few days ago when I noticed that in bright sunny day, driving my daughter to her daycare, that the lights are ON and do not want to turn themselves off. I said to myself... great, another sensor gone.

The direction of my travel to daycare is away from the sun. I arrived at the daycare, and parked the car facing sun (happened to), and when I returned and started the car, the lights didn't come on (auto-headlight worked.)

I did some search and found out this is a common issue (if you can call it an 'issue'). I moved to California from Canada, where all cars have daytime running lights, and frankly, I think it is safer to drive in daytime with your lights on anyway (I ride a motorcycle that has by default headlight on all the time.) Anyhow, this behavior of auto-headlights in X5 does not bother me.

I must say though... every car that I have had (including 10+ year old shitty ones to newer 2002 Mercedes) that have had auto headlight, didn't seem to suffer form this kind of problem, and could detect (very very reasonably) whether it was light out or not, and would turn on/off while passing under the bridges and such in a very acceptable manner. It seems like BMW is either trying to separate itself from others, or simply doesn't care about getting this thing right (like their many other electrical/sensor issues that I and every other person I happen to talk to who has owned a BMW complains about.) I have not noticed this behavior in my wife's 328i though... I would not be surprised if that behaved the same... I just don't drive that car enough to notice these things.