
Many thanks to EvanEvery (FA) for this incredibly useful mod with write up & pics:
by EvanEvery
Its a very simple mod - all you need to do is splice a switch into a wire easily accessible under the passenger seat!
Here's the details: The Vehicle Speed Signal is sent to the NAVI Control Unit under the passenger seat via pin 28 on connector B207. This is a Grey Wire going into the Grey connector on the front of the NAV unit under the passenger seat. All we will need to do is splice a switch into this circuit to disable the VSS signal and you will be able to perform NAV system input. While you make input, the vehicle will appear not to move on the map. Once you are done, flip the switch to complete the circuit again and the system will then take a few minutes to recalculate your vehicle position.
There are two large connectors fitting into the NAVI unit under the passenger seat, one is White and one is Grey. The one we want to modify is the GREY connector. Here is a photo of the NAVI unit under the passenger seat as viewed from the front (My splices are already in place in this photo). Note the large GREY connector on the right:

The Inifiniti Shop Manual on page AV-136 shows this connector as well as the VSS signal on pin 28. The shop manual on page AV-149 provides a description of this signal and circuit. Here is a diagram of the pinout of the connector as viewed looking at the connector on the end of the cable:

The easiest way to get at this connector is to remove the trim from around the front seat and swing the harness out to the side. In order to remove the trim from around the seat you will have to:
1. Pop the little trim window out of the front of the seat trim panel. This is easy to do if you push with your fingers from under and behind the "window". Then remove the two screws on either side underneath the little trim "window"
2. Pop off the little trim plate which covers the location where the seat belt is fastened to the seat. Then remove the single screw under this panel which holds the larger seat trim panel to the seat.
3. Start to swing the large seat trim panel around from the front to the side of the vehicle. You will see a little white connector which snaps the trim panel onto a seat retainer post. Carefully unsnap this connector from the retainer post by popping it off with a screw driver. Do not try to unsnap this connector by pulling on the seat trim panel.
4. Then just push the trim panel a littl bit to the rear of the vehicle and will come right off.
Now just reach under the seat and disconnect the Large Whit connector, the Large Grey connector, and the small Grey Connector. Swing the harness out under the seat to the side where you can get at it.
Cut the Grey Wire which connects to pin 28 (see diagram above) and insert a SPST (Single Pole Single Throw - On/Off) switch and some additional wire so you can position the switch somepace handy. All this switch will have to do is either complete the circuit we just cut (for normal operation) or open/disconnect the circuit (to allow NAV input while driving). Here is what my connector looked like after I spliced in my switch with some 3M UY connectors:

Currently, I have my little switch just poking through the trim "window" on the front side of the seat trim panel. Its real easy to get to and I dont have to cut up or drill any of my interior. Perhaps I'll move it to a more permanent location sometime later:

This mod works great! It just takes a couple of minutes for the NAV system to fully catch up with the vehicle location once the VSS signal has been interrupted. Best of all its easy to do and you don't have to take down the dash or glove box!
edit by particlefx: added the pdf version