Firstly, a couple of questions.
You mention OBD pin 4 & 16 are at 12V nominal but pin 4 should be a ground, it might just be me being daft as you also say you have leds illuminated on your interface.
Is the 'P' illuminated next to the shift lever when the ignition is on at any time?
If it is on the CAN bus is normally active.
I think if you are resurrecting an ED3 battery pack you need to look at the Xentry / Vediamo combination with Tactrix type J2534 Passthru OBD interface already discussed on the forum or at least the Arduino based Battery Diagnostic tool, I think both can give valuable information for an ED3 in this condition.
It all started for me with a Hackster post of this guy in Germany who created a device to interrogate the status of the main battery in his smart Electric Drive car.
The 'universal' scanners I have seen either don't work at all or produce confusing messages because the P codes from the the defective ED3 HV system are not typically seen by a 'universal' scanner.
It is hard enough interpreting the P codes using Vediamo which translates the original factory message to English with some German thrown in but it works well once you get used to it.
Xentry on a virtual machine works well and is the same software as the dealer uses and allows you to view various signals and clear most codes.
I also gibbered on about Xentry/Vediamo/J2534 method in previous posts and it is also where someone also mentioned using a Mucar Vo6 with an ED3 'add-on' but I have not used it :-
Hello everyone, I have 2014 Ed and today I disconnected the HV battery so I could fix my heater. When I finished and Plugged the HV battery back in I have the HV message, and do not tow and drive system engine off. The HV battery is fully charged and the 12 volt is too. Any advice would be great.