Error 02 - WARMING UP
HP LASER PRINTER ERROR CODE 02 - WARMING UPHP ERROR CODE FOR 2, 3, 2D, 3D
1. I/O Cable is bad or hooked up incorrectly. Communication problem between computer and printer. 
HP LASER PRINTER  3SI, 4SI 
1. Defective display cable or formatter PCA. 
HP ERROR CODE FOR 4V, 5SI 
1. I/O cable is hooked up incorrectly or bad interface in Computer. 
2. Defective parts such as: fuser, PCA board, DC controller.

Error 11 - Paper Out

1. Paper tray empty or not seated correctly. A buildup of toner on the edges of the tray which slide into the printer can sometimes cause problems. Take a sharp tool, like a razor blade and scrape the buildup off these edges.
   
2. Sensor Arm Stuck or Broken - check for free movement of the sensor arm. On the LJ4/4M/4+/4M+ the sensor flag can get knocked out of place when a paper jam occurs and the tray is pulled out abruptly. Most times this can simply be reinstalled. If it's broken, you will need to replace the sensor flag
   
3. Defective Tray Size Sensing or Configuration - Most trays have tabs which depress a series of switches when installed. Verify that the tabs aren't damaged and that the tray switches located in the printer are not damaged. You can depress these by hand and hear them click. Occasionally the contact for the micro switch will get bent and will have to be replaced. Also verify the configuration through the menus on the printer.
   
4. Defective Paper Control Sensor PCB - These do fail and will need to be replaced
   

Error 12 Printer Open

1. Paper path door (IIP/IIIP) or top cover open. On the IIP/IIIP this can be caused by a defective toner cartridge, defective cooling fan, PS4 or PS5 sensors. Also caused by the density adjusting PCA located behind the density adjusting slide switch.  This board takes the input from the two sensors and provides info to the DC controller. If the board becomes defective, you will receive an error 12.  Easily replaced after removing the top cover and three wiring harness connectors. If you want to attempt board level repair try the electrolytic capacitor, C702, 10 uF 50 VDC.  On the 4P/5P printers, the top cover is open or no toner cartridge is installed. This error can also be caused by a defective interlock switch assembly.
   
2. On the Laserjet 4/4+ an error 12 can indicate the top cover open or a broken tab on the cover assembly. On rare occasions a defective paper control assembly or actuator can cause this problem. Verify the tab on the cover is not broken
   

Error 13 Paper Jam

1. Check the paper, make sure it meets the paper specifications for your printer. Tractor feed paper with the edges ripped off doesn't seem to work very well. Extremely heavy or thick paper is also a problem. Check the HP paper specification guide for more info. Be careful with labels, use only labels designed to take the heat generated by the fuser assembly. Regular labels my "ooze" adhesive as they pass through the fuser assembly and literally gum up the works! Also check for any partially peeled labels, this can be a disaster if they come off inside the printer.
   
2. Check the paper path for toner or paper dust buildup. Look for bits of paper lodged in the path particularly around the sensors.  4L/4P printers can have paper stuck in the pickup area which is accessed by removing the screw over the oblique roller cover.
   
3. You may have a worn pickup roller. Common on the LJII/III series is a worn input pickup roller. Sometimes you can clean these and get a few more miles out of them but when you start to get jams with a smudge on the top middle of the page, it's time to replace both the input pickup roller assembly and the cork paper separation pad. On the IIP/IIIP you can wipe toner/paper dust buildup off the roller and also remove the separation pad (small cork pad) and clean it as well. If the rollers are glazed or you see cracks, replace the roller or assembly. Replacing the pickup roller and seperation pad on the IIP/IIIP will quiet the chatter associated with a worn seperation pad.
   
4. Is the paper size correct? Is the software set for the size you're using? Is the menu set for the size you're using? Check these items.  If the software tells the printer to expect a different size (legal, A4, COM10) than the tray available, you will get an error. This can happen when printing a FAX document formatted for A4 size paper.
   
5. You could also have a defective or dirty exit sensor. Replace or clean as needed.
   
6. Make sure the paper cassettes are installed correctly. A buildup of toner on the edges of the tray which slide into the printer can sometimes cause problems. Take a sharp tool, like a razor blade and scrape the buildup off these edges.
   
7. Bad paper pickup solenoid. On the LJII/III series the rubber damper on the clutch release solenoid can degrade and become sticky and gummy. You can remove it and replace it with a piece of adhesive backed felt. Note: A sticky solenoid can also be the cause of text appearing lower on each successive page.
   
8. Bad drive gears. Again on the LJII/III we are starting to see more and more failures of the gear drive assembly. A broken tooth on one gear is all it takes. Replace this as an assembly.
   
9. Listen for the motor operation, make sure it's operational. If not replace the motor or drive circuit as required.
   
10. HP IIP/IIIP and Apple Personal LaserWriter's that pickup the paper and then crunch it up at the toner cartridge usually have a bad drive gear assembly. If the paper crinkles right at the toner cartridge it is most likely the drive gear located on the right side of the printer. If you fold down the right side cover, you will see a white gear/clutch assembly. Replacing this should solve your problem. You need RG1-1777, Drive Gear Assembly.   Take a look at the white gear - if it looks as if it has twisted on the shaft that is the problem. You can remove it and rotate the inner white gear - it should exhibit a one way clutch action and rotate smoothly. The outer gear should rotate in one direction only with a spring action which limits it rotation.