Unless you have lots of chipmunks or mice residing in your yukon, it's probably not the wiring.
If this Bose amp is like the Bose amp in my old Armada, then there was a power relay that died, causeing the rear speakers to die (the Armada had a button to purposely mute all rear speakers for quiettime in the back. It was like a $5 part to swap out, and all was good.
Maybe searching for the amp part number & "rear speakers silent" or something like that will point you in the right direction.
Does the subwoofer run off the signal to the rear speakers?