I have a 2004 Yukon Denali, bought the truck new, now has 200,000 on it, we love it. A similar high pitch chirping sound appeared a couple years ago. It seems to be coming from under the dash, and happens with or without the stereo on. It is different than the ringing sound you hear if a door is open or another type of warning comes across the system, for example seatbelts are not on.. It drives us nuts. I took it to the dealer and of course while there it would not reproduce - they don’t want to put the time in it.. The minute I drove away it started chirping again. It also happens with or without the air conditioning on. It is usually a single chirp and the interval can be anywhere from one minute to twenty minutes . Replaced the key fob batteries, that did not seem to help . it would be nice if GM could comment on what this is.

 

Did you have any luck solving this?
Mine is exactly as you described, but I’ve noticed it makes the same sound randomly even when the key is not in the ignition, with the doors closed and locked.

It sounds like a “alarm active” chirp.

 

I also just bought a 04' silverado and had the exact same beep, i knew it used ro be a fleet vehicle do i check for a tracker that could be low on battery and there was one