There are only 2 real paper path sensors on the 2150. The first will be just above the paper tray behind the feed rollers and the other will be inside of the fuser. I would contact dell support if you are in warranty. The fuser can be replaced if that sensor is damaged, only takes one screw to remove, but the one above the paper tray is tougher to service. Hopefully there is just a small scrap stuck in the sensor and your error will clear.