How can you fix code E21 on your Nordictrack treadmill?

To fix the E21 error code on your NordicTrack treadmill, first, power off the machine and unplug it for a few minutes. Then, check for any loose connections or damaged wires, especially around the console and motor. After inspecting, plug the treadmill back in and power it on. If the error persists, consider resetting the treadmill or consulting the user manual for further troubleshooting steps, or contact customer support for assistance.