I am having the same issue with my 2018 Jeep GC with the 8.4 " Uconnect screen. Have been to the dealership several times. They finally rep;aced the Amp. The problem came back yesterday and went back to the dealer. Numerous codes stored for speaker issues, video input etc. They don't seem to have any idea what could be causing the problem. Tone is constant while in AM FM SAT mode, goes up and down with volume. Can not use radio when tone is present, to annoying ... drowns out radio. Was present for 3 - 4 hours yesterday. Wonder if it could be a short in the antenna since it is only present in AM FM SAT mode. Very frustrated with this vehicle, have had other quality control issues with it. Would like Chrysler to contact me.