Pretty sure they are a non-serviceable item, going to need to replace the whole rack. The metal used has a tendency to enlarge itself over time and start to leak, making replacing the seals impossible.
Everything you have described above are all normal operating temps and pressures. Not sure what would set the CEL off with it being at a normal idle pressure.
Dumb question, have you manually folded the mirror by hand to see if that "resets" it? Or listened to the mirror when trying to fold it to see if you hear anything working, by trying the switch on the driver's door panel with the passenger's side window down?
Just a shot in the dark without the video, seems like you think the noise is coming from the front of the engine. If so, have you checked the water pump pulley to make sure there is absolutely no play in it?
Will not work properly
The GM TPMS will not work properly if one sensor has a dead battery. The TPMS relies on the sensors within each tire to continuously monitor air pressure and transmit data to the receiver module. A dead battery in any of these sensors can disrupt the entire TPMS operation, leading to inaccurate tire pressure readings or the complete loss of communication with the receiver module. This can result in the TPMS failing to detect and alert the driver of potential underinflation or overinflation in the tires, posing a safety risk on the road.
It was going happen even if they did not shut off the 3 that were still working.
My factory screen for the stereo decided, along with many other parts that 7 years was enough and died. I replaced it with a new factory unit (used my GM points from all my repairs, so no money out of pocket), huge difference in the quality of the backup camera. Maybe the camera is not really the issue, maybe the "wonderful" touch screen is actually the problem.
Think the temp info is probably vehicle specific. You just put these on the valve stems, put your truck into learn mode, then walk around the truck with the GM specific tool in the picture (comes with kit, and I already had one), touch each sensor until the horn honks, on to the next one, when you are done with all 4 you get the double honk. TPMS light goes off on dash, pressure shows up again in the DIC, and even shows on the OnStar app.
Mine died after 7 years, waiting to replace my tires, then do a set of factory sensors at the same time. While I wait, saw these and gave them a shot. They work just fine, but are pretty ugly because they are kind of big, but work just as good as the OEM, and you can replace the batteries.
If the price is right, I would do it. Chance the power function may work on the door, maybe even the turn signal. Don't think the heated feature will work because that button is located with the HVAC controls, and you probably do not have the heating grid on your back window. Worst case scenario you will have better looking mirrors.