some TCU modules did not have BT even when BT info was printed on the label...

I have installed BT on '98 E39, 2002 and 2006 E53... I don't remember much about E39, it was gazillion years ago, but 2002 E53 needed a voice recognition dummy plug, but the 2006 did not need that dummy plug... maybe you need that dummy plug?

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E53 X5 4.6iS
147K mi - Sold May 2013
Tireprints left in:
USA, Nicaragua, Costa Rica, Panama, Russia

E53 X5 4.8iS built 2005-10-17
66200 mi - June 2012
96000 mi - June 2013
112000 mi - June 2014
OEM fire extinguisher
OE first aid kit
OE tow hitch
OE TV module
OE aspheric mirror
K&N air filter
black/white badges
rear camera
4-channel video recorder

Here is the list of things I have done to the X