All of a sudden, the beeps that go off in the cabin, sound is very low. They were fine a few days ago, I looked in settings but could not find anything about the sound level. The system is on (button to the left of steering wheel). Anyone know of a setting to make the beeps louder?

 

Haven't heard of this one before.
Since the parking system is shared with coupes and sedans, you'll probably get more attention posting in those sections.

 

The way I understand the Sonar System, the volume varies based on the distance detected between the sensor(s) and the "obstacle." The closer you are to the object the louder the warning sound (4 levels for center sonar sensor and 3 for corner sensors). The volume is not "user defined."

Does the Sonar OFF Switch blink when you turn the car/ system on? Does the icon on the center display turn on/ indicate distance under normal conditions?

It is possible you may have a sensor going bad that is interfering with distance detection. Any evidence the rear end may have been bumped- in a parking lot perhaps?

Unfortunately, short of scanning for any trouble codes within the sonar system, there is not much you can do to diagnose the issue.