Generation 4 – 2014 OBD Port K-Line Troubleshooting

So I got a VAG COM KKL adapter to try and use with the RomRaider and could never get it to work (trying to find the culprit of a p0420 code, see pgs 144-145 of P0420 Diagnostics) and so ordered a another cable to think about I got a bad cable but it still didn’t work. Then I was looking in the service manual I have (I turned off ebay a while ago, I don’t know how legal it is) and following his procedure, with the ignition on (engine off) pin 7 reads 9.1V which according to this is bad.

Looking at the cable, it looks like pin 7 and 8 are shorted (which looks like this is required on some other vehicles after a quick google search). I removed the short so it’s just pin 7 connected to pin 7 but no luck. Pin 8 seems to be the ignition power so it goes up to 12V when the ignition is on and I think it may have shorted something somewhere.

It looks like the k line goes to a number of different places. I think the problem could be with the ECM and something shorted to 9V there, but I suppose it could be either of them.

Any thoughts on the best approach? Do the electronics use k-line to communicate with each other or only with the external device?
I’m thinking maybe the best approach would be to try removing the k-line pins on each of those connectors (starting with the easiest to reach) and see if the voltages drop (to 0 V? or slightly below 5 V?).
Another option would be to try removing the ECM and looking at it (which I’m thinking is the problem). I’m an electrical engineer (work in avionics) but it’s a little scary to remove the ECM and mess around.

Does anyone have any other thoughts?

CAN works fine as my OBDLink MX+ still works.

Thank you.