Hum...."P0685 - Engine Control Module (ECM)/Powertrain Control Module (PCM) Power Control Circuit Malfunction"
Diagonostic procedure clears the DTC and sees if it reoccurs. Intermittent DTC indicates a loose connection in IGP line connectors...if the DTC does reoccur, "intermittent failure, the system is OK at this time"...if it reoccurs "Update ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known good ECM/PCM, replace the original ECM/PCM."
Note that the HDS is required for these actions, does this independent mechanic have a HDS?
There are actually 2 ECM relays, at about $35 each...and one ECM at about $540...
You can tell the dealer no, but the relays are yours and yours alone after you buy them (that's the usual electrical parts policy). If it's a relay, figure the diagnostic cost should about cover the repair...if it isn't, your independent can't save you any money if he doesn't have access to an HDS unit. Even then, it's not likely to be a massive cost savings. I like independent mechanics, but this screams dealer.
On the Navi, not sure. That is not a listed error, try entering diagnostic mode and checking things out:
If battery has not been disconnected (you are not at code or gps aquire screen);
Ignition switch on, press and hold "Menu", "Map/Guide", and "Cancel" buttons together for 5 seconds...it will go to diagnostic screen.
If the battery was disconnected and you are at either screen above; hold down "Menu" and "Zoom out" buttons, then at "Navi Link Screen" push joystick to get to "Functional Setup menu", the touch "Return" icon to get the menu.
It's a very useful trick!