When the "lube belt" error code appear on the console, you can try to lube the running belt firstly. If error code still exist then replace a new console circuit board. "lube belt" error on Horizon T101 CT5.4 Treadmill often caused by the console circuit board, part number is 1000300283 S102-11.

Links as below: https://anytreadmillparts.com/products/treadmill-screen-circuit-board-upper-controller-1000300283-for-horizon-ct5-4-treadmill?_pos=1&_sid=a2211e55f&_ss=r