My x5 3.0i 2006 t won't start this morning but temperature, gas level clock were wrong so I turn the engine off and restart a couple times it won't start and I saw message trans. false safe program on for 5 second . I wait 15 minute and restart , gas level and temperature was back as normal and doesn't show any message any more but it won't start ??? Does it mean the battery run out?

SOURCE: BMW X5 Trans Fail Safe Program,

sometimes it will clear if you turn the X5 off and restart it. however, it could be an early indication that the tranny is about to expire. i have had it happen and it cleared with a power cycle, but also had friends where it cleared for a few weeks/months and returned. this time it was really the transmission that went bad. if you can't get it to clear, then i'd suggest taking it to the dealer and have them plug into it to have a better look.

SOURCE: x5 trans on

Before you start looking at the transmission, make sure that your battery is in good shape and the battery terminals are making clean connections. The transmission computer is quite sensitive to voltage variations.
If the problem is in the transmission, the most common failure point that I have read about is the temperature sensor. They sometimes fail after a few years. The sensor is not expensive, and not too difficult to replace, and it was time to change your transmission fluid and filter anyway, right?