just purchased a bs02 and 500c display. Installed,etc, but throttle will only power on for a few seconds and then shuts down. Have entered password and gotten additional screens, but still shuts down right away. Display has a warning with exclamation point with speed on it, but have not reached speed listed. Any ideas about what I have forgotten to do or where problem may lie?
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The motor will turn itself off if it is not detecting speed. It sounds like it’s some thing related to the speed detection system, make sure that the monitor is correctly detecting speed and that should take care of your issue I would assume. 
I hold down the right button for a couple of seconds, "hello", comes on, then,I enter 0,0,0,0, left button 4 times.
you may want to program the controller and double check all display settings are set right for your bike specs, will need a bafang prog cable. check these guides https://electricbike-blog.com/2015/06/26/a-hackers-guide-to-programming-the-bbs02/ https://edrivenet.com/bafang-programming/