[ltujustas]

Hello. I need some help. I have a issue with a Q7 etron and I'm wondering if there are people who understand the Audi HV system.
The original inverter stopped working properly and stored a P0606 internal control module fault. With the old inverter, the car only starts once - after that, communication with the inverter is lost. If you turn off the car, it won't start again and the cluster shows SAFE. However, after disconnecting the 12V battery, it working again. 
At the same time, when communication is lost, it also logs P2533 Ignition switch/Run start position circuit: Open or short to ground.
We replaced the inverter with another one (not yet adapted to the car) but the same issue occurs - communication drops and p2533 appears again, but this time new inverter without p0606. 
Does anyone know where the ignition switch is located ? What exactly should we look for ? We've already disconnected everything - engine ecu, hv modules, hv battery - but as soon as p2533 shows up, communication with inverter is lost again. 30/15 terminals fine on inverter, all fuses fine.
If need, I can provide a video showing exactly how it happens - you can clearly see in the measuring values that the 12 supply just drops, and right after that, dtc p2533 appears. No matter what, after 3-5 minutes the issue repeats - 12v drops and p2533 appears