<p>Before it stopped working, the stepper motor worked very well and didn't show any problem. I experienced this after I fixed a filament problem. The filament got stuck soI retracted to pull the filament out of the heat nozzle. But when I finished this, the extruder didn't work anymore...</p>

<p>I restarted the system but it didn't work. All the motors work fine, even the extruder motor. The A4988 driver has the right voltage at 1.0&nbsp;-&nbsp;1.2&nbsp;V. I have already replaced my RAMPS shield and AtMega board, but it still does not work! I changed the extruder motor to another axis port and it worked good. The voltage input is stable at 11.2&nbsp;V</p>

<p>I can't figure out why the extruder motor is not working for the extruder port?</p>

[{'answer_id': 13493, 'author': 'user77232', 'author_id': 12857, 'author_profile': 'https://3dprinting.stackexchange.com/users/12857', 'pm_score': 0, 'selected': False, 'text': '<p>When you pulled the filament out of the extruder you most likely induced a voltage back into the stepper driver which fried it.</p>\n'}, {'answer_id': 13498, 'author': 'DrPortgas', 'author_id': 20389, 'author_profile': 'https://3dprinting.stackexchange.com/users/20389', 'pm_score': 1, 'selected': False, 'text': '<p>I have found an answer. So dumb\u200d♂️\u200d♂️. It need to heat up nozzle before use extrude or retract command</p>\n'}]
['https://3dprinting.stackexchange.com/questions/13491', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/20389/']