techboy99, do you have more information on those pinout changes you had to make?
I am trying to do the same thing you did with a rear only PDC. I have an e46 rear only PDC module. I have already gone through the long beep and replaced a bad sensor. Everything connected up and coded the rear only 4 sensors in BMW Scan 1.4. Now I only get no errors in BMW Scan but no sounds from the system.

I did put the car in reverse and verified each sensor is working an clicking when you move near.

Maybe the grounding change is all that I need to do next.