Sorry. Its the Navigation... But again, funny thing is it gets loud once I open the door like something is up with a switch or something in the door...
It's more likely software based vs hardware as the audio pilot mic only compensates for when the engine is running
Now the radio has a vss(vehicle speed sensor) feed in the smaller of the two harnesses that plug into the radio
I kept my old radio when I upgraded of the op wants to try it and see if it helps or not
Also keep in mind the chimes volume is seprate from the radio and onstar volume
Try it with the onstar system running and see what happens(that will help me figure out where the problem truly is)
Fyi the onstar will keep the radio and amp going even with the key removed and the door open(tried it myself) and it works no matter if the system is active or not(mines not active)