You will need to check the speed sensor for proper alignment, cleanliness and function. it should be located near the front roller or mounted on the motor. It should be within a credit cards width of the magnet or 3 credit cards width of the toothed wheel. You can test these manually by turning the walk belt by hand and look to see if there is a blinking LED light on the motor control board. If there is the sensor is working and if there isn't the sensor needs replaced. If the sensor is good do the following:

Remove the Motor cover and do the following:

# XXXXX a 12-18 volt dc battery fully charged(like one from a cordless drill)
# XXXXX sure it is fully charged, because it won't work if not
# XXXXX the + and - to the motor red is + and black is -
# XXXXX the motor turns slowly your motor is ok, if not the motor is bad and would need replaced
# XXXXX the motor is ok then your motor controller(the board with the metal) is malfunctioning and would need replaced.