Here's what I did. You can try it too, but I'm not responsible if you damage your stuff or burn things. Please be careful. I don't provide any guarantee that this won't destroy your car, kill your dog and everyone you've ever cared about. But it worked for me, and while I still have a wife, we never had a dog.
This is the summary of what I'm doing to the Bluetooth Control Unit Wiring Harness - after it is completely disconnected from the Bluetooth Control Unit. As for the unit itself, I'm going to take it out of the car entirely, because it's another ~16 ounces to carry, and who knows, maybe that's another mile of range. Or at least a few hundred yards?
In short, I bridged the Mic Input + to the Audio Out + (same for the "-"), bridged the Steering Wheel Control wires in a similar manner, and provided 5v+ to the Microphone, which was not getting 5v from the BCU any longer.
Now, last time I pulled the car apart, I didn't take any photos. But this time I did.
If you want to do this, you're going to need
*A Display Audio Unit from a wrecked 2015 Sentra (you can source from a wrecker, eBay, or Car-Part.com
*An AX-NIS-ADDCAM1, wired as described above (mic input signal (pins 24 & 25 on male end) to their new location on the new radio (pins 50 & 52) plus all un-used wires removed. The ADDCAM harness has a RCA plug that I didn't need so I removed it; I may have had to move some pins around but I don't remember. You will be able to figure this out easily when you're checking the "straight through" part of the harness. I also ran a new wire to the trunk (if you have a multimeter you could potentially try re-using the old "AV COMMUNICATION HIGH or AV COMMUNICATION LOW" pins which aren't used any longer) to carry the +5v from pin 51 to power the Mic. This wire was connected to Pin 29 of the Bluetooth Control unit harness. I IMPLORE YOU TO DOUBLE CHECK MY PIN NUMBERS FROM THE SERVICE MANUALS (2014 LEAF & 2015 SENTRA - select "AV"), AVAILABLE ON NICOCLUB, BEFORE YOU WIRE THIS STUFF UP!
Speaking of checking pins, you'll see this illustration all over the service manuals:
What this means is that pin numbers are counted as though the pin is connected to the device - that is, you are looking at the cables going into the plug, with the pins pointed away from you.
*A philips-head screwdriver
*Either of the following:
-A method to remove pins from the wiring harness (I used a T-Pin, which you should nick from someone's office cubicle because they probably come in boxes of 1,000), or
-a soldering iron and wirecutters
*A spudger/plastic pryer (to remove trim)
*A socket-wrench (or other wrench-like thing) and 10mm, 13mm, 16mm sockets. 10mm is optional if you want to remove the BCU, but you can just leave it there, disconnected and skip the 10mm
*A multimeter is handy
recommend you keep the Nicoclub Service Manual handy for instructions on removing trim, or referring to if you have questions about the wiring. it is a thorough pain to remove trim under even the best circumstances, and these manuals help to understand just how to do it.
UPGRADING YOUR STEREO STEP 1
: Remove the rear seats (yes, seriously).
Once you've got the seat base up, use your 13mm socket to remove the seat back sides (lol):
...and your 16mm socket to remove the seat back base (bronzey-colored bolts in the center).
See those two wires on the left? I think they're part of the charging circuit. Good Lord don't damage them.
Be careful not to pull the seats all the way out of the car - moving the seats just a half foot forward meant I didn't have to disconnect the seat heaters, which is one less mistake to make putting things back together again.
: Access the Bluetooth Control Module (a.k.a. dead weight)
The reason we needed to get the seats moved was because their presence prevents you from removing the rear side interior trunk panel (U.S. passenger side) and thus, the BCU. Before you can get to that panel, though, you need to remove the rear inner trunk lining: two little push pin things hold it in place.
With that out of the way, you can finally remove the panel blocking the BCU. As you get it loose from the wall, disconnect the little luggage lamp.
Here's the BCU, as I left it last week - with functioning telephone & bluetooth streaming - but no steering wheel controls.
This is it with the jump made between pins 7 & 9, and pins 8 & 10.
Time to remove all that tape and do some testing of the theory I penned above.
Remember: Safety is our #3 goal.
Looks like crap but IT WORKS!
Shall we tidy it up a little bit?
Good enough for me. Let's ditch the BCU & wrap the harness in a quarter-roll of electrical tape.
Installation is the reverse of happiness.