If that is the original TCU, it should not have Bluetooth according to SIB 841304:

"E46, E83, E85 and E53 vehicles produced
between 3/2004 and 8/2004 are equipped with a
TCU that does not support Bluetooth. On these
vehicles, the TCU can be replaced at the
customer's expense with a 2005 MY TCU.
Cradles may not be added to these vehicles
because of wiring incompatibility.

Please disregard the Owner's Manual insert,
shown to the left, indicating Bluetooth
functionality. The hardware in these vehicles
will not work correctly."

The SIB indicates the seat belt needs to be fastened on E53 X5 in order to initiate the pairing procedure. I didn't find this necessary on the TCU that I retrofitted.

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2010 X5 3.5d: SOLD, but miss the torque...
2004 X5 4.4i: SOLD, but served us well