PDC Advice

[Helihover]

My pdc has never worked. It sounds like its a pretty cool feature and I would like to get my pdc system up and running. I have no scanner tools (inpa,ect. ) except for an obd reader which will do me no good in this case.

When I engage the car in reverse, the dong comes on emitting a solid tone and the pdc light flases. From my understanding this is telling me I have a fault in the system.

So far all I have been able to do is physically check/listen to the eight sensors. All four front sensors emitt the "clicking noise" and only one of the rear sensors emitt the noise. I suspect my fault lies somewhere around these three sensors. I have physically checked the connectors on theses three sensors and nothing changed. The connection being closest to the sensors.

My questions:
Is there another location that I can check at the rear for proper connection besides the connection right at the sensor?
If you were in my shoes would you just throw three pdc sensors at it? I don't want to do this as these are a little pricey.
Is there a way to test ohms or voltage at the connector/sensors?