Are you sure the motor itself has not failed?
While very rare to happen, it is not unknown.
Use a multimeter to check the winding resistances.
They should be about the same on both phases.
You can measure them at the motor or at the end of the cable where it plugs into the control board (probably easier).
I have had similar issues and it has always turned out to be a partially or completely clogged nozzle and/or threaded connector tube between the heater block and cooler.
You didn't mention doing any of these things so I thought I'd suggest them-
* Remove the nozzle entirely and see if filament can be fed through the tube freely. If not, remove the tube also and try feeding again
* If removing either or both of them fix the problem, clean (or preferably replace) them. I have had lousy luck cleaning nozzles personally, so I just replace them.
* If you have not done so already, make sure that the filament is retracted automatically a few mm at the end of every print. That way it will not sit in the nozzle tip and carbonize. This is particularly important for PLA, but even for ABS (I have had issues with both of them).
* Finally, if you do replace the nozzle, I suggest using stainless steel ones. Others may disagree with this choice, but they work quite well for me.
In case you don't know how to do the automatic retraction, just add this to the "end code" gcodes in your slicer-
G91 ;relative positioning
G1 E-5 ;retract the filament 5mm to release some of the pressure
Do this before you turn off the heaters of course.
Once again, 5mm is a distance that others may disagree with, but it generally works for me.
Even 2mm will relieve the pressure on the nozzle but 5-10mm will get the filament away from the very tip end of the nozzle where it is most likely to clog.
I hope this helps you.