2020 gmc Sierra 2.7l bought with 9k miles on it. Now with 46k miles. Same exact issue. Installed new brake pads and rotors on rear. Pistons wouldn’t fully compress. Turned in with Allen key. Replace all but had to put back on outer rear pads. Replaced sensor on driver rear pad sensor and what do ya know! Still system monitor fault. After having ball joint go out while driving and left steering knuckle 33k miles almost crashing and this now, plus other stuff. What a waste of 46 grand on a new truck.