Easy enough repair to get my bluetooth back
Il Mio Problema
Had long ago spilled liquid in MBP 13". All that suffered - eventually - was bluetooth, which always displayed a greyed-out icon in the menu bar.
La Mia Riparazione
Pretty straightforward, following the guide. I should have done this sooner. There was some visible greasiness to the old airport card, which I guess was from the liquid damage. Everything worked fine on restart.
Il Mio Consiglio
Note: you may have to reauthorise your computer on iTunes at it seems to use the airport card as part of the system ID.