For the error code of 3. The front lower cover needs to be taken off the front of the treadmill. There are 4 phillips head screws. Please unplug the treadmill first. When standing on the treadmill to the right side, there is a plastic wheel with hoes in it. When the wheel turns it goes threw a sensor. Either the wheel is not on the roler, the wheel is broke, the sensor has been knocked out of it position or the sensor is broken.
Andy, January 2010