CR-10S Three year experience user.
My extruder stepper quit running. I went through the usual troubleshooting, swapping cables between axes ect. Every cable checks out and works fine on another axis and every stepper Including extruder works fine in another axis. That is, the extruder stepper will step fine when connected to the x-axis driver. Nothing will work when connected to the extruder connector on the board.
So I assumed the driver on the board was shot and purchased a new board. (eBay Original Creality CR-10S 3D Printer Motherboard Control Board DC 12V) and I still have exactly the same problem. All cables check out on another axis, all steppers check out on another axis, no output from the extruder channel on the board. Exactly the same as I began! HEEEELLLPPPPP