I'd like to upgrade my 2014 Up! radio to a VW Up OEM model that has DAB and Bluetooth support. I've been told Bluetooth might be built into the car ECU and not be part of the stereo, in which case it's a no go. Any ideas if that's correct?
BT is normally built into the radio unit; I'd be surprised if it was in the ECU - it will have to deal with digital audio bitstreams, and then analogue audio via a DAC, the latter being already present in radios, so it doesn't make engineering sense to run the extra cabling. But what you may have heard is the radios are 'keyed' to ECU (or BCM), and any change of unit will require recoding, and probably some 'feature unlocking' from a computer like vagcom etc...
Thanks freemansteve, I did find it odd that Bluetooth would be built into the ECU but my local car audio place didn't seem that confident on it. I actually have a salvaged higher-spec radio unit without the security code - the local dealer has quoted £30 to unlock it - that must include the pairing you mention.
On the earlier Up's with the RCD215 radio, the bluetooth is part of the Maps & More unit, so if you don't have a connection for it on the dash, you won't have bluetooth. You can fit a later RCD215 with DAB on it, as I have one in my 2013 High Up I retro-fitted, but its not a cheap unit to buy from VW.