I have a Precore 835 Treadmill and am getting error 37 and error 44.

The error 44, is usually loose connections. Specifically, the incline potentiometer. It is recommended that you check the wiring.

With error 37, the unit will need to be reset. In under ten seconds, have the safety key removed and reinserted twice while the treadmill is powered.

This means to pull the safety key, reset it, pull it again, and reset it again.

Then your console should tell you it is resetting. After about five seconds or so, it will fully reset and come back on like normal. Hit start and the treadmill should operate normally.