This problem is that the wire of the extrude motor is loose .
Firstly, do a pull and insert of the plug, make sure it's tight .
Secondly, pull and insert the plugs of the three cables at the right side.
Thirdly, open the y-box and check whether the wire of extrude motor is loose .
Here is a video link for how to open the y-box .
Lastly, plug the extrude wire.