Odd rear PDC problem
 

On my 04 4.8is my parking sensor throws a fault when reversing and one of the sensors is activated. The fault is for the “gong” or chime speaker. I found the speaker disconnected so I replaced it and it still won’t work. The fronts are fine and function correctly without error. The rears will cause the little speaker to click and the pdc led to flash an error. I bought another chime speaker and tried it and it too does the same. All sensors are clean and clicking when in reverse. I’m stumped. Anyone have any pointers?