I think it is the neg (-) (left side) also has a safety wire attached to it that should be secured to the terminal in a specific configuration and be very tight as not slip and fall out of that specific position {QSilver 7 will be posting soon with the battery terminal diagram hopefully with proper name of said safety wire}.

The purpose of the wire is to act as a safety in the event of an accident. It has a tiny charge like the seatbelts and will disconnect power to the car.

Should you have inadvertently manipulated this wire either out of place, or not secured it perfectly it could a) either short causing a code, or b) short cutting power c) other gremlin type errors.

I don't think it has been mentioned yet but if you are not sure when the battery has been replaced, replace it now. year 2005 would dictate that if it is original that is a likely culprit. Also, given that year even if it were replace in '09 it is probably good measure to do so. I have found unlike other vehicles the X will not show signs of a weakening battery i.e. slow or no starts with a jump or two, but will show gremlins everywhere instead.

I doubt it is the terminal connection, but wanted to post in the event that what appears to be a deadening battery issue with a 4x4 light that should go away either in a short period of time or by the clock to clock method doesn't solve. Good luck.

And... are you working with any good indy's here?

__________________
'14 X1 7000 miles

Hasta luego a

'10 X3 3.0 55k miles
'09 335i 55k miles
'08 528i 94k miles
'09 Mini 88k miles
'06 X5 3.0 112k miles
'04 X5 3.0 128k miles
'99 528i 120k miles