Eplus ebike drive uses RS-485 protocol for communication.
display/controller is a master, battery electronics and motor electronics are slaves.
when you press power button on dis/controller first thing it try to make "hand shake"with batt electronics and motor electronics, simply they have to report to disp/controller.
when batt electronics doesnt respond to display/controller inquiry it displays ERROR 1.
but it does many attempts before displaying ERROR1