Help Locating/Repairing BCM on 2004 Xterra

[STunedSER]

I bought the Xterra from Nissan Dealer Used over 2 years ago just finally got a remote for it. Xterra will not go into Programming Mode and dealer stated the BCM is not appearing on OBDII device.The Xterra's Security light does flash and when doors are locked with window down and door is opened the alarm does turn on.

Questions I have are;

Where is it located?

If it was unwired/disconnected how to reconnect?

Thanks in Advance