well i just bought a nardi steering wheel and it comes with wires im pretty sure its black and red make sure to hook the wires up correctly if not that maybe you disconnected the wires somewhere els sorry i dont know alot about electricity but i hope it helped.
on my 01 teg i have a single wire coming from the srs harness that is the positive lead for the horn, i just tap that into my momo steering wheel hub and i'm good to go. i believe obd2a has a different srs harness, since im obd2b