Greghennings

I'm troubleshooting my rear door speakers. When I bought it they didn't work, all factory stock. I changed the head unit and speakers and still nothing. I ohmed the old speakers and they were all good. I tried to ohm out the speakers at the head unit, I can get 4 ohms out of the front but not the backs. It would seem that somewhere between the head unit and the speakers there's something disconnected. Does anyone know of any connections between the two that could have came loose?