So here's my idea to bypass the Navigation lock-out and avoid having to slice and dice any of the factory wiring:

I need to find a replacement factory male harness as well as a female harness (perhaps one that is usually used for installing a different head unit, but with NO factory wires omitted). I would then soldier the two harnesses together and plug one end into the factory harness, and the other end into the radio/navigation. Any cutting and soldiering and other destructive stuff would all be isolated to the patch of wires between the harnesses. This way, I could use the methods explained by others to create the parking brake/speed sensor bypass without damaging anything stock. See the beautiful MS Paint schematic I drew up below.



I have no idea where to get these harnesses I need. Any help is appreciated, as well as comments/suggestions for this idea.

 

That looks good, but I believe the Parking brake to ground, also has to be switched, like the VSS wire. You can do both wires with a DPDT switch, no need for that relay stuff, talked about elsewhere.. Let us know if you find a source for your "Plug N Play" Cable.

 

Thanks for the input, you make a good point. So I don't need a relay or anything, just run the VSS and the P. Brake wire from the radio to the switch and have the "on" setting ground them and the "off" setting patch them thru like there was no switch present? This simplifies things alot... If I can find these harnesses I will def. try it.

 

I may be wrong, but I don't think you want to ground the VSS wire, just have your switch disconnect it from the Radio/Nav Input.

 

AFAIK, the connectors are not industry standard. To build a harness would mean you need to pull the female connector out of a broken head unit which are still kinda hard to find. You will also need to rip the harness w/male connector out of a wrecked car.

 

Make your own