When my harness connector shorted out, the transmission stayed in fail-safe mode for the last 200 miles of our trip. It would start out in second gear, then shift very methodically (slow) up through the other gears. It did not engage the lock-up clutch though so fuel mileage definitely suffered. But I could tell the transmission was operating in such a manner as to protect itself. I wasn't overly concerned, because it was the third time I had experienced the condition after going through a car wash or very heavy rain.

2002 X5 3.0 259,850 miles
2004 325i 115,000 miles