an image forming apparatus includes a device for setting the apparatus in a check mode to check a state of the apparatus and for selectively executing one of a plurality of check operations . in one aspect , each check operation is set using a commonly provided numeral key , and the check mode is unconditionally released using a clear key . in another aspect , one of the check modes includes a test movement of a movable member used in image formation . in still other aspects , sheet transporting operations are controlled based on the location of a sheet jam , or based on the selection of a sheet sorter . the state of each of the image formation devices is checked even if an improper state has already been detected , plural error states are repeatedly displayed in a specific order , and a display unit is commonly used .