OBD Plug wiring for Polo 6V5 (APQ)

Hello first time user here, I have a 98 polo variant (6V5) with an APQ engine, i'm trying to get the diagnostic working but I suspect someone before me messed up the pinout on the diagnostic plug, I tried one generic OBD scanner and it got power but can't connect to the ECU. I would be grateful if someone could upload or tell me the pinout for the plug, I have 4 wires and the colours are the folowing: one thick red wire, one thick brown, one thin white/gray (I think i'm slightly daltonic), and one thin yellow. Additionally if someone could also give a schematic so I can trace if everything is ok with the wiring regarding the two thin wires I would also be grateful! Thank you!