Pork loin in slow cooker
Loin or tenderloin is a very lean cut of meat and should not be cooked in a slow cooker.

Slow cookers are better suited to cuts of meat with high amounts of connective tissue, like pork shoulder or chuck roast, that turns into gelatin as it cooks for a long time.

IMHO, tenderloin should be grilled or broiled just until the center is 145° or so. Then rested and sliced.

Good luck!