Error: "936 Main Drive Motor"; Error: "936 Transport Motor"; Error: "937 Main Drive Motor"; Error: "937 Transport Motor"
The 936 and 937 error codes indicate that the printer thinks there is a problem with the main drive motor.
If your printer is posting one of these errors, turn it off and let it sit powered off for at least a minute.
While the printer is off, open all of the doors and covers on the printer. Also remove the toner cartridge. Make sure there is no paper jammed in the printer. Pay close attention to the area where the toner cartridge sits. The main motor is located just to the left of the toner cartridge.
If nothing appears to be wrong with the inside of the printer, reinstall the toner cartridge and close all the doors and covers. Now power the printer back on. If the error does not return, try printing again.
If the error does not return when you print, continue using the printer. If the error does not return after a few days, this may have been an isolated incident and the printer should be fine.
If either the 936 error or the 937 error returns after you power on the printer or when you try to print, the printer will probably require service. The main motor assembly may need to be replaced.