While a dual speed (HS/MS) CAN OBDII interface would be ideal, with Forscan installed on a laptop, a basic OBDII reader should give you some codes that you could begin diagnostics. It really seems odd that there is no apparent DCDC support.
So some people have found that the telemetrics system can screw up 12V systems, and they advise to just remove fuse F1 in the rear fuse box. In the trunk on the driver side is a large rectangular panel, behind it is the fuse box. F1 is a 5 amp fuse in the upper left corner. Don't reinstall the fuse.
The service manual also says to check F22 in the under hood fuse box, to the left of the 12v battery. When you check the fuse, completely remove it. F22 is the fuse for the battery monitoring system. Sometimes when you do a jump start or charing of the 12v battery the monitoring system can get confused. It does not control the 12v out of the battery, but the possibility of charging of the battery by the DCDC converter. You can reinstall this fuse.
If you remove the big black foam cover under the hood, the DCDC converter is to the RH (passenger) side of the vehicle. It has the high voltage orange cables connecting it, the thick low voltage 12v cables, and a signal/logic cable. You can safely check the low voltage 12V cables and the signal/logic cable.
Check if the low voltage cables are loose or can move when wiggled. Disconnect and then reconnect the signal/logic cable (top center). The orange high voltage cable requires you to take some safety precautions first. After disconnecting the positive terminal cable from the 12v battery positive terminal, you can remove the low voltage cables from the DCDC converter and inspect for corrosion or arching. After shutting off high voltage, you can check the orange high voltage cable. You can disconnect it, and then reconnect it, checking that it is very secure on reconnection. Pay close attention as it is most likely a 2-stage design. If you partially disconnect it and you do not fully remove it, or if you fully remove it, but do not fully connect it, you might get HVIL errors, and the vehicle probably won't even start. The thick orange wires are for the high voltage, the thin orange wires are for the HVIL.
The reason you are checking the connectors is because there is a possibility that they are loose, or corroded. You are disconnecting them to make a visual inspection of this situation. If the low voltage cables are corroded, you can clean them up yourself with sandpaper or a cardboard fingernail file. If the high voltage connector is corroded, it is best to let the dealership clean that. Mind you, it might be necessary to replace the HV cable if it is severly corroded. Though you might be curious, do not touch the metal surfaces inside of the connector. Your skin oil can adversely affect the quality of the connection.
To remove the black foam cover, use a plastic trim tool, or a pair of butter knifes to pull straight up on the center "button" inside of the "volcano". It has to raise about 1/2 inch before it will release from the bracket underneath the black foam cover. Do this for both buttons. Once the buttons are up, pull up on both buttons to release the clips and enable the black foam cover to be removed from the bracket.
To install the black foam cover, position the cover so that the buttons kind of seat in the holes of the bracket underneath. Push down on the volcano, and while doing so, push the button down. It takes a little fiddling around to get the buttons into the holes of the bracket.
To shut off high voltage. open the hood. open the rear passenger door and flip forward the rear passenger seat. Disconnect the positive terminal cable from the 12v battery, and position it so that it cannot mistakenly make contact with the battery positive terminal. At this point, the vehicle must be completely "dead". Wait 5 minutes. Behind the rear passenger seat is a small black door, flip that down. You will see the orange high voltage disconnect. Press the white clip and raise the black handle about to 45 degrees. Press the white clip again and continue to raise the handle to 90 degrees. Separate the disconnect from the battery pack. The vehicle high voltage is shut down. But you must still be cautious. Also here, do not touch the metal plates of the disconnect, as your skin oil can adversely affect the quality of the connection.
To power back on high voltage, place the disconnect back onto the orange socket of the high voltage battery. While pressing it in, release the white clip and lower the black handle from 90 degress to 45 degress. Press the white clip again and lower the handle all the way down until it clicks. Put the black cover back on. Return the rear passenger seat back to its riding position. Reconnect the postitive terminal cable to the 12V battery positive terminal.
Know that most EV techs at dealerships don't know that much about the electric power train. Sadly, they will be guessing and just throwing parts at a lot of the problems that happen with EVs. This is why you read so many postings of how it takes so long for the dealer to solve the problem.