Plug simple stepper motor NEMA 17 on E2 slot of the main board on Creality CR10

I have build a Syringe Pump with a simple stepper motor (NEMA 17), and now I want to actuate it through my 3D printer.

I successfully replaced the main extruder with it and it worked, although I had to still warm up the hot end as Marlin doesn't want to actuate the extruder at cool temperature.

Anyways, I am realizing that my Creality CR10 v3's board has a slot for a second extruder, so I would like to plug the syringe pump there.

I did it but when trying to control it through OctoPrint, I have an error saying that my printer reported a default.

I guess it's not plug-and-play, and it's probably complaining about the absence of second thermistor and so on , right?

What should a complete newbie like me do to be able to control E2 with just a stepper motor connected to it?

To prevent extrusion at cold temperatures, you should enable the feature called "allow cold extrusion" using G-code M302 S0.