All of the sensors checked good with a digital multimeter. I ended up replacing the main PCB board, and the problem remained. After reading about common Samsung problems, I defrosted the refrigerator. My coils weren’t a solid sheet of ice like others have described. There was frost on every component though. I used a hair dryer to speed up the process. The whole refrigerator may have been in pieces for 2 hours. I’m not sure I needed the board, but the refrigerator is working now, and you don’t fix what’s not broken.