What is wrong with my Horizon T101 treadmill?
After lubing the treadmill belt of my Horizon T101 treadmill, my treadmill is not working. I pushed the belt to move it manually and went really fast then slow. It kept changing speeds. Also when not manually pushing on the belt to move it there is an E1 error. Could it be the speed sensor? Any advice on how I can fix it? I'm going back to school and don't have much now.

Comments
I would check the mechanical and feedback sides separately before assuming the motor controller is bad. With power disconnected, make sure the walking belt/deck and drive system do not have excessive resistance. Then check the speed sensor alignment, magnet/trigger and cable connection.
If the belt never starts under its own power, the motor/controller path is more relevant. If it starts and then stops after roughly 10 seconds with E1, loss of speed feedback becomes more likely.
I put the diagnostic sequence I use for the Horizon T101 E1 symptom here:
https://www.fitnessmachinehelp.com/horizon-t101-e1-error/
It should help separate the likely causes before buying another part.