What does the error 3 mean on my treadmill?

this is what is said on the sportcraft website:

E3 – No speed sensor reading. Unit shuts down. This is the most difficult repair diagnose. The speed sensor is connected to the frame of the treadmill near the drive pulley on the front roller. There is a small magnet on the side of the pulley wheel. The sensor tip must be no more than 5mm from the magnet. If for any reason the distance is greater than 5mm the treadmill will shutdown.

Mikhail
July 2010