There is another possibility that I have discovered just this evening.

My Sony Ericsson P910i has been not working at all in my 2005 X5 4.8, yet works perfectly in my 2004 X5 3.0.

Now that I know it is something to do with the car, I just have to figure out what is different between the two to create a possible configuration that works in the 2005 models......

So for starters, before I go on down to the dealer, can anyone advise how I might check the TCU details and software versions?

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2006 E53 X5 3.0D
2004 E53 X5 4.8is
2004 E53 X5 4.4 Sport
2011 E70 X5 3.0D with Aero kit
2009 E71 X6 50i Sport
2009 E70 X5 50i Sport
2007 E60 540 M Sport LCI (All time favourite car)
2007 E70 X5 4.8i Sport
2005 E53 4.8is
2003 E53 3.0 Sport