ERROR 14 No EP Cartridge or No Toner Cartridge

• No toner cartridge or cartridge not fully seated - pull it out and install it again. On the IIP/IIIP the connections for the high voltage are made on the left side of the printer so you may want to favor that side as you install the cartridge.
  
• On the HP LaserJet/LaserJet Plus (2686A/D) this can be caused by a defective cassette micro switch in which case you will have to repair or replace it.
  
• On the II and III Series printers, this error message can be caused by a faulty paper control PCA. This is the board mounted to the DC power supply which is in the right front corner of the printer. Press the spring contacts and listen for the micro switches. You should hear a definite clicking.
  
• On the II and III Series and the IIISi/4Si, make sure at least one of the two drum sensitivity tabs are present. These are small rectangular blocks of plastic which contact the switches in the printer.
  
• On the 4V/4MV check the toner cartridge micro switch on the High Voltage PCB - SW501.
  
• Also on the 4V/4MV check the door open sensor (PS402) on the terminal board located under the transfer roller.
  
• Can also be caused by a defective DC controller. Pretty rare though
  

Error 16 Toner Low

• Toner cartridge is empty or toner in cartridge is not distributed evenly. Gently shake the toner cartridge both from side to side and from front to back. This can generally get you 100 or so more pages.
  
• Bad or dirty cartridge contacts. Look for the conductive contacts on the cartridge and the corresponding contacts in the printer and make sure they are clean and free of contaminants.
  
• Defective High Voltage power supply or on the LJ II/III the DC controller to High Voltage power supply can be defective. Check for opens on the cable.
  
• IIISi/4Si check the door open sensor flag, PS1. Also check the toner level sensor and the toner cartridge itself for damage. It can also be caused by a defective DC controller. You can verify this by substituting a known good DC controller if possible
  

Error 18 MIO Not Ready

• The printer is not connected to a LAN when it's expecting to see a LAN. Terminate the port on the printer with a BNC T and two 50 ohm termination's.
  
• The MIO card is defective or maybe just not seated correctly. Remove the card and reseat it, try swapping with a know good card from another printer. Replace if necessary.
  

Error 20 Memory Overflow

• A large print job has exceeded the memory capacity of the printer. Verify that the SIMMS or memory cards are seated. Add more memory or simplify the print job. Remember the original HP Laserjet has only 128K of memory available, the LJ+ has only 512K and neither one is really upgradable.
  
• On the 5P turn the image adapt and page protect to ON or AUTO. These can be set within the Remote Control Panel. Press GO to resume printing.
  
• On the 5L, set the Enhanced I/O to AUTO (PCL mode) and resend the print job
  

Error 21 Print Overrun

• The print job is to complex. Simplify the job by removing font changes etc. On the III, IIID, IIIP, enable page protect if you have and additional 1 MB of memory installed.
  
• On the 4/4M/4+ and 5: The print job is to complex, enable page protect from the control panel and from the software. You may need additional memory.
  
• 4L Same thing with to much data or the page is to complex. Simplify the print job. Turn the image adapt and page protect to ON or AUTO either from the control panel or from within HP Explorers Remote Control Panel.
  
• 5P/5Si Same as above, Press GO to resume printing.
  

Error 22 / I/O Config Error/ Par I/O Error/MIO Error

• I/O configuration for the computer or printer is incorrect. Configure is properly.
  
• Check I/O Cable, it could be the wrong cable or damaged.
  
• Is the computer on?!
  
• How about the I/O port - damaged, seated properly, pins not bent?
  
• 4+/5P/5 The computer and printer aren't talking because of improper signal protocols. Could be a bad cable or loose connection or just a poor quality cable. Reseat the cable and use only high quality IEEE 1284 compliant cables.
  
• 5Si Are you using a non-HP MIO device?