If your OBD2 scanner isn’t connecting to your car’s internal diagnostics, it may be due to a K1 or K2 line short to ground. Here is a good way to troubleshoot what’s causing the problem.
My car is a 2003 Audi TT Quattro, but many other OBD2 enabled cars will have a similar setup, especially Volkswagen/Audi brand.
One of those wires will be the one that loops back into the main loop to go to the OBD2 port, so be sure and leave that one connected the whole time. After you’ve identified the troublesome K line, you can find out which module it came from by connecting to VCDS and seeing which module you can’t connect to anymore. You can either replace the faulty module if it’s essential (ECU, ABS, etc) or you can just leave that particular K line disconnected if you haven’t noticed any other problems. You can then twist the good K line wires back together and secure them with a twist cap and redo the wiring sheath as well.