HP LaserJet 4000

• Code: 40
• Display: 40
• Description: Make sure computer and printer are set to the same baud rates. Reset as needed.
  Check the MIO card, remove, clean contacts, reinstall. Replace if defective
  An abnormal connection break may have occurred during data transfer - Press Continue or Go to clear this error message.

• Code: 43
• Display: 43
• Description: This indicates a communication problem between the formatter PCA and an optional interface installed (such as a network card). Remove and reseat the optional interface card. If the problem continues, remove the optional interface card and set the printer for standard parallel interface by taking off-line and holding down "Menu" key for 5-10 seconds. Scroll through items until "I/O =" appears and use the +/- key to display parallel and the enter key to select. Then put the printer back online and send a test job from the host computer via the parallel cable. If this is successful, you have a problem with the optional I/O card and should replace it or reset it.

• Code: 50
• Display: 50 Fuser Error
• Description: defective heater, termistor, termoswich, triac

• Code: 51
• Display: 51 Loss of
  beam detect
• Description: Improperly seated toner cartridge - remove and reinstall
  Laser shutter blocked or damaged
  Damaged fiber optic cable
  Defective Laser PCA - replace
  Faulty Laser Scanner Cable Connectors - Remove and Reseat connectors
  Defective Laser Scanner Assembly - Replace

• Code: 52
• Display: 52
• Description: incorrect scanner speed and is generally the same as an error 51.

• Code: 55
• Display: 55
• Description: On IIISi/4Si Printers this is due to the DC controller not receiving the proper information upon startup. Check the connectors on the DC controller and power supply. If you don't hear the motor immediately and you don't have a paper jam, change the power supply.