Blown e-box fuse

[isarkisov]

Hi guys,

I am perplexed as to what is going on with my 2001 X5 4.4i. It all started with 'Service Engine Soon' light turning on. I decided to take it to my father in-law (he owns a shop). On the morning before taking it to the shop 'Service Engine Soon' light turns off, but I took it anyway just to read fault codes. We found O2, Thermostat, and some other misc. error codes (don't remember them all, but there were quite a few). My father in-law said that he was going to clear all codes, have me drive for a while, and then if 'Service Engine Soon' light turns on again we'll scan again to figure out what exactly is causing light to turn on.

Two weeks pass by and 'Service Engine Soon' light turns on again, only to go off again within couple of days. Then while driving on a freeway it started smelling like rubber or plastic was burning, and white smoke started filling the cabin from the front. I stopped immediately and opened the hood. Smoke subsided, but it still smelled like something has burned or melted. I tried to start the car only to find that my RPM were going up and down so I stopped the engine.

I tow the car to the shop. By the time it's in a shop it wouldn't even start. I just turn they key and it wouldn't even crank. One thing I noticed was engine temperature gauge going all the way up (engine isn't even hot anymore)

Anyway, my father in-law calls me next day and tells me that F1 fuse is blown in e-box (according to him it controls ECU, Transmission Control Unit, and thermostat), and Crankcase Ventilation hose developed a hole; so he goes on and replaces both hose and the fuse. Car starts just fine... 4 days later... fuse blows again, RPM jump up and down, and it smells again.

Something is blowing F1 fuse The problem is that it doesn't happen right away, it works fine for a while and then blows. Can it be thermostat malfunctioning? After all there was thermostat error code. Another weird thing was 'Engine Control Fail' message on instrumental panel after fuse blew second time, and of coarse all error codes were deleted. We are thinking about replacing thermostat next, but at this point it's very difficult to diagnose due to problem happening intermittently.

Any ideas? Please help!