e53 is a 2000 - 4.4i with 118K miles
Coolant Thermostat Heater failure: Blew Eng. Electronics Fuse F1
This failure has been discussed in other BMW forums that use the same characteristic MAP thermostat heater. Suggest Google it.
The water pump, thermostat, and thermostat heater was original so the thermostat heater failed on a cold morning and in doing so, it took out the engine electronics fuse F1.
See vfwjed thread
http://www.xoutpost.com/bmw-sav-foru...rmostat+heater
If your older X5 has the original water pump and thermostat assembly, recommend replacement of both ASAP. At a minimum, inspect the thermostat heater; Pull the connecter off look for signs of burning. I might even suggest unplugging the heater as a temp measure to prevent a meltdown of the heater itself along with the engine electronics fuse F1.
Thankful the ECM was not damaged.. only the fuse.