I haven't heard back from you yet - please reply and let me know if you still need assistance with this.
The E5 sensor error indicates a problem with the speed sensor.
First, check to make sure it is clean and positioned correctly. If it is located close to the front roller it should be 1/8" away from the magnet but if it is located off the back of the motor it should be clean and centered.
You can test the motor - see below. If the motor is good look at the motor control board and manually push the walk belt and see if there is a blinking light on the board. If there is the sensor is good if not replace the sensor. If the sensor is good and the motor is good replace the motor control board.
To test the motor:1. Get a 12-18 volt dc battery fully charged(like one from a cordless drill)2. Make sure it is fully charged, because it won't work if not3. Attach the + and - to the motor red is + and black is -4. If the motor turns slowly your motor is ok, if not the motor is bad and needs to be replaced5. If the motor is ok then the motor controller board is malfunctioning and needs to be replaced.