How do I turn off the PDC when parked?

[xDrive35d]

Here's the scenario. I pull into a parking space. Either forward or backward. I put the car into reverse at some point either backing in to a space or aligning the car when pulling in forward. Since I have put the car into reverse, the rearview camera and PDC (parking distance control) system activates. Then I put the car into park. Here comes the problem. If I leave the car running, such as waiting for someone, talking on the phone, eating lunch or whatever, the PDC keeps beeping at me when it senses the curb or something. I have tried pushing down on the i-drive knob and turning off the camera system, but the PDC sensors keep beeping forever. The only way I have figured out to stop them is to turn off the car completely and turn it back on again. It seems to be that they should stop beeping when the car is put into park.

Something wrong with my car? Or something wrong with my ability to understand the owners manual?

Thanks,

Dave.