First post. Fixed trans fail safe error.
 

I just got a '03 X5. Had it about 2 weeks, it's awesome. Yesterday I was driving it in some pretty heavy rain and got the dreaded "transmission fail safe program". I immediately thought it was due to a electrical issue, prolly wet wire connection. I searched: trans fail safe in rain . I saw several posts about this issue. The most liklely suspect is the TCU has gotten wet. I opened up the e-box and saw standing water in the unused cavity of the control. I took the control out of the car and took it inside and opened up the box to expose the circuit board. Sure enough, I could see water has been getting in to the circuitry by the mild corrosion and stains. I shook it and a bunch of water droplets flew out of it. Then I took a hair dryer to it for 5min. I sealed up the case with electrical tape as a preventative measure. Put the control back in, started her up, and lo and behold : no more fault. Drove her around the block as the theme song from the movie "Rocky" played in my head. Thank's xoutpost .com. The posts in this forum helped me through this issue.
I have had several BMW's in the past. The one before the x5 was a '88 750il with the m70 v-12. So I'm no stranger to "the BMW way" and working on these cars. Here are some pics I took.

If it wasn't for the wet electronics. Usually trans fail safe mode is due to a faulty alternator. Spiking up to 15-17 volts.

Yes. I called my mechanic about it and the was the first thing he asked was; "is the battery weak" ? I knew it had something to do with the rain, the trans isn't going to just go out just like that. It's going to act up for a while if there are any major issues with it.
Thank God for the internet forums. All mass produced cars have inherent issues that will eventually pop up. My computer is my #1 tool.

Get some electrical contact cleaner from rat shack and spray the connector. Those pins looks pretty corroded.

http://www.xoutpost.com/attachments/...sed-uppins.jpg

Good job on tracking down the problem. Its not always moisture or voltage issue causing the Trans Program Failure mode. I was routinely getting the Trans Fail Safe mode,usually when shifting from neutral to reverse or drive. Finally checked and found a P0709 code, Trans Range Sensor, circuit intermittent as the cause. I replaced the neutral safety switch, a $250 item (Airtex) and solved the problem. Nasty electrical gremlin, a little water in that switch and corrosion. I could have disassembled and repaired the switch, after I removed and had a chance to look it over, but didn't have time to mess with it and potentially have the car down. Happy the switch on side of trans is easy to access and replace. Only sting was the cost of a simple selector switch.