Hi, I recently decided to upgrade my ender 3 printer to dual extrusion. Everything is now working, apart from the fact that my 2nd extruder refuses to move at all.

Im using marlin v1.1.9, on a MKS GEN V1.4 board. everything else is stock from the ender 3, apart from the new extruder motor, which works perfectly when swapped with the original one. In short, i am confident that its definitely either the board or the firmware, neither of which i am very knowledgeable on.

The strangest part is that if i move extruder 1 using the move axis menu, say to +10mm, extruder 2’s position is then also at +10mm when i go to change it, and vice versa. There is also an option under move axis for “extruder”, “extruder 1”, and also “extruder 2”. I don’t know why this is, but if i change the value of one of those options, both the others change by the same amount. Changing the value under the “extruder” or “extruder 1” options both move extruder 1, however changing “extruder 2” does not move anything.

I’m super stuck here, and any help at all would be really appreciated.

Do you have two heaters for each nozzles, or just one? If you have one only, the Cura can’t handle single nozzle. You will need to remove any gcode reference to T1.