Hhhhhmmm, the loom can be done in such a way that you dont even need to touch the K Line, literally plug the loom into yr fusebox and the obd port works as it should. I would say that wire needs splicing into yr existing OBD port wiring, pin 7 on the obd port.
Any diagnostics that can clear codes will do, I know theres a few 'Read Only' vag tools out there.
That K Like is gonna need to be connected before you can clear anything tho.
I would contact Vagtronics to double check about the K Line scenario before taking my word on it, as I said before, our looms are OBD plug and play so im not 100%
