This is an old thread but glad I found it.
Had the same thing happen to me about 2 weeks ago on my CPO 06 530xiT. I first saw the rust on the test drive in the back left corner panel. Asked my CA about this and he said "not to worry about it"
Car came from TX. Lot's of humitidy down there. Take car home and all is good. Get windows tinted at the place the dealer recommends. All is good. Take it to the recommended dealer car wash and all is not good. Get the SOS malfunction error message and nothing works. Make appointment at the dealer and take it in on a Monday. 2 days later he calls and tells me that the electrical is fried because of water. Asked how this happend and he asks me when I got the windows tinted. Explained to him they have been tinted for only 2 weeks. Tells me that the window tint place jacked this up and it is not covered under warranty, going to cost me over 700 dollars to fix. I explain to him that your dealership recommended this place and there is no way that if there was any water left over would rust in 2 weeks in Colorado with single digit humitidy in January. He tells me that he will "try to push through to BMWNA"
Get a call the next day and tells me that he has found the issue. Clogged drains. Asked him how to unclog them and he tells me that they will have to force air and liquid through them to get them clean. Tells me that they drain in front of the rear tires on both sides. There are 2 holes that can drain. One that you can see in the front of the sunroof and one that is not visible. Ask how we can stop this from happening again and he tells me not to park under trees....nice job dude!!!! There is no way for the consumer to test this or do any maintenance and just hope that they can use the internet to find an answer.
They keep my car for 4 days with cleaning, reprogramming and working on this so it does not happen again. I show up on Friday and all is good. Ask to speak with a Service Manager and they tell me that they have all left for the weekend...at 330p. I am just glad that my dealer covered this under warranty and they now have a record of this. If it happens again, they can cover this again.
Below is a link for all known SIB's for for newer 5 series but did not see this one on that list.
Good luck to everyone that has had this issue. Print out the SIB and take with you to the dealer. They cant deny thier own recall can they?
2006 530xi Touring - Titanium Silver Metallic with Black Leather interior - Cold Weather Package - Sport Package - Premium Package - Logic 7 audio - Comfort seats - Ventilated cooling seats - PDC - Adaptive Xenon lights - Navigation - Heads Up Display - 35% Tint all around - Full Thule roof rack - Child seat and baby seat
Winter setup - Rubber mats - rear trunk mat - Thule box - 17" wheels