2015 Yukon XL Radio silent with no available volume control showing, hands free call volume ok, and chimes work and voice assistant works full volume

[grandpianodave]

I bought this 2015 Yukon XL 175k miles from dealer with the radio "not working".  No volume comes from speakers when playing fm/am/xm radio.  But other things seem to work, kind of.

 

The display shows the station or xm station playing, but volume control on steering wheel or volume knob on distplay does not show the volume level or adjust it.  I've gone into the simple menu and tried all the deeper volume controls.  Many times.  If I push the 'Mute' button on the right side of steering wheel I can see volume bar in the dash and it stays at 0% no matter how I try to adjust steering wheel volume paddles or radio knob.  I've turned auto volume to every setting including off.  

 

The hands free phone (bluetooth link) gives me ok volume for the caller's voice on the other end of the phone through the windshield speakers.  This volume is adjustable on my iphone but not with volume paddles/knob.

 

When I push the icon to 'voice control' radio ("Tune to 620 AM") the radio assistant voice is loud and clear asking me to say a command.  Comes through Windshield and door speakers.

 

The microphone works fine for calls and radio voice control.

 

The chimes, blinkers sound work loud and proud.

 

CD player no volume and truck has no rear DVD player, so can't test different source.

 

(I don't know if it matters, but a religious sect (Hutterites, like amish people) owned it before me and all they did was road trip relatives back and forth from south dakota to pennsylvania with this vehicle. Could they have disabled radio somehow to keep devil's music out of the car?)

 

When I bought it the dealership was in the process of taking the dash apart to troubleshoot, but they sold it to me just before pandemic for $14,750 if they didn't have to do any more work on the vehicle.  So they stopped what they were doing and but everything back together.

 

I put a new battery in vehicle, no change.  Would this negate having to locate a fuse?

 

As I kind of understand there are different radio/sound modules and a Bose power amp. 

 

Anybody had this problem or know which modules I should be swapping / re-flashing?  Do I have to flash them to my vehicle if I buy them off Ebay?  Can I do it with a scan tool readily available, or is it too hard to learn how to use the tool?

 

Thanks!!!