HP LaserJet 4345 MFP / M4345 Formatter Issue or Blank Control Panel

Like most machines built in this time period, the formatters in these machines are known points of problems. In this article, I’ll talk about the various problems you’ll see when the formatter has issues and how to go about troubleshooting  to verify you are ordering the right part.

Types of Formatter Issues

  • Blank display with one, two, or three of the attention, data, or ready lights lit up solid or blinking.
  • HP logo hung on display or constantly moving but never going to a ready state.
  • Stuck on memory cycle, display goes blank after memory cycle or there is a row of asterisks or blocks on the display.
  • Warm up or initializing stuck on the display.

These are the main formatter issues I’ve seen or read about on this model. I’m sure there are more possible results so if your issue isn’t listed above continue reading.

Note: These machines do take time to complete their power-on sequence. Some customers get impatient and think they have a problem when they don’t.

Troubleshooting and Repair

Before removing any parts make sure to unplug any communication cables and the power  cord to prevent additional damage.

These machines have a formatter heartbeat LED on them. The LED is located under the parallel or USB port depending on the model. When the machine first powers on, the light should blink then continue blinking after the Memory Count has completed.

  1. Unplug the power and reseat the formatter.
  2. Remove and reseat formatter accessories like extra memory, hard drive, phone card, and firmware. The M4345 series doesn’t need memory DIMM and firmware as these are part of the formatter board. Also these machines will function without the hard drive plugged in. Additional features like scan and, I believe fax, will not be available if hard drive is not plugged in but the machine should boot up and test pages will print.
  3. Reinstall each device one at a time and see if you get different results from the control panel.
  4. Reseat Control Panel Cable from control panel display and DC Controller.

If none of the above has worked then remove the formatter and run an engine test print.

  1. Turn the machine on and let it warm up for a few minutes. The engine test print bypasses the formatter and verifies the DC controller, Power Supply, and other devices are functioning the way they should. The print engine test should print off a single sheet of vertical lines. The test will only work if all the covers are closed, paper is installed in the tray, and if the machine doesn’t have any other error states like paper jams.
    1. If this test fails then the next step is to check the power supply located in the middle of the machine.
    2. If the test passes then the next step is to replace the formatter. Find the location of the engine test button below. I typically use a straw from a can of air to activate the button.


In the 4345 MFP – replace memory (Q2627A), firmware (Q7725-67996) and formatter (Q3942-69011)

In the M4345 –  replace the formatter (CB425-67911).

Make sure to take accessories such as firmware, extra memory, hard drive and phone card off the old formatter and transfer them to the new formatter when replacing it.

When you install a new formatter, information such as page counts, serial number, and install date are stored in NVRAM located on other boards inside the machine so make sure to not turn the machine off until the information has been completely transferred from one board to the other. Also, if you take a formatter from another machine and install in into this machine you might run into problems as the information stored in the NVRAMS on the boards conflict with each other. Not a good idea. It’s best to replace the formatter with a new or refurbished one to avoid unwanted problems. Email addresses are stored on the Hard Drive so the only thing you should have to configure is the Network and user settings on a new formatter.

Display problems are typically related to the formatter and its accessories but the ECU or control panel can cause similar problems. If the engine test doesn’t work then replacing the ECU is probably the next step you should take. Before running the engine test make sure the formatter is removed as it can cause the engine test not to work.

Formatter issues can happen at anytime. The one that caused me to write this article happened out of nowhere. I was servicing a machine for lines on copies and feed issues through the ADF. I installed an ADF PM kit, reset the counter, and noticed the print engine was past due for a PM. I turned the machine off to check the fuser and swing plate gear for wear and tear. After doing so I plugged the machine back in and turned it on. The only thing that happened was the internal fans moved and the ready and data light on the control panel came on solid. After doing all the troubleshooting above and having the engine test print out fine, I found the formatter had gone bad. I went out the next day with a new formatter and the problem was solved.

HP 4345 MFP

Flash (Firmware) Q7725-67996
Memory Q2627A
Internal Hard Drive J7948-61031
Formatter Q3942-69011

HP M4345

Formatter CB425-67911
Internal Hard Drive 5851-3833


Engine Power Supply RM1-1041

Kevin Gumpp is a certified printer technician and freelance writer for Market Point. If you have a question regarding this topic or have any other printer repair related questions or topics for which you would like more information, please send an email to maryp@marketpoint.com.

7 thoughts on “HP LaserJet 4345 MFP / M4345 Formatter Issue or Blank Control Panel

  1. Hello, I am having the HP laser jet 4345 mfp since 24th Oct 2015. its printing quality is very good. But from a week it is showing ” Initiallising Scanner” , “Paused” and “Checking Printer”. Please help me and guide.


  2. I have a HP 4345mfp and I am having the initializing scanner that is the display. My question is how can you tell that the formatter board is bad? I can see the heartbeat light, from everything I’ve read is that if you can see the heartbeat light then the formatter board is functioning? Also is there anything else I can check as I about ready to give up on this thing… Any help will be appreciated..


  3. Hello,
    I’ve M4345 MFP that displays “Inflate failure send RFU upgrade on usb dev port” followed by “Downld file now send RFU upgrade on usb dev port”
    I’ve downloaded the latest update utility from HP and tried to send the firmware over USB after having installed the driver for the “Hewlett-PackardHP LasterJet USB Upgrade” printer that is detected by default.
    But when I send the firmware, nothing happens on the computer or on the printer. I’ve tried various other things but still same outcome.
    Do you have any ideas for me?


  4. WHOA, hang on… I’ve had to clean up a mess after someone else used a similar process and continued on after the formatter replacing most of the boards. $1000+ in parts alone. …then the customer called me.

    If you have a “blooming logo” that never resolves, the most common cause is the NVRAM. Not the chip – the settings data. Replacing boards, would NOT resolve this problem because the NVRAM gets backed up on multiple boards. This is also why you can’t use a ” working pull.”

    If you have good engine test, 2 heartbeat LEDs, but get stuck at a perpetually blooming (moving) logo:
    * Do all the above hardware troubleshooting, but BEFORE YOU REPLACE ANY PARTS:
    * Cold reset.
    * If that doesn’t fix it, then NVRAM reset.

    In most cases that will fix it – no parts! Configuration settings will be lost, but as they were corrupted, that’s unavoidable. This process is among the things mentioned in HP doc c00598346.

    Also, note that sometimes on these models you have to hit the engine test TWICE.



      • hi.. I have 4345 printer and I bought new last 2 days starting good result and printing but now mechine is turn on & HP logo contenous running after they start but never ready & cheaking printer erros disply on screen others scanner are working but printer is not ready and mechine’s out roller is contenously moving.. please help any one I am much in Tension


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