HP Laserjet 4100 series service mode

1 While turning on the printer, hold down SELECT and CANCEL JOB until all of the lights on the control panel are lit.
2 Press the right side of the MENU key, then press SELECT. The message SERVICE MODE temporarily appears and will reappear when the printer completes the initialization process.
3. Press [Menus] once to display SERVICE MENU.
4. Once it says SERVICE MENU press ITEM to scroll through service mode items.
5. To exit the service mode, press GO.
Note: If READY appears in the control panel, the keys might have been released too soon, or the wrong keys were pressed.