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Lexmark T640

Lexmark T640

Dark toner haze or fog printout check

What you will see

The page/envelope has a "haze" or "fog" of toner covering it. This makes the page look as if it has a gray background. Follow the instructions below to try to diagnose and resolve the issue.

Test the toner cartridge

In most cases, the cause of this issue will be the toner cartridge.



Power off the printer and remove the toner cartridge. The toner cartridge can be accessed by opening the upper front cover of the printer.


Install another toner cartridge into the printer. Depending on your specific circumstances, use one of the following methods:

  • Install a brand new toner cartridge, if you have one available.
  • If this is a newly installed toner cartridge, reinstall the old cartridge you removed when you installed the new one (if possible).
  • Install a working toner cartridge from another Lexmark printer of the same model.


Power the printer back on.


Try printing again. Print 20 to 30 pages to give the toner background a chance to clear. If a different toner cartridge corrects the issue, the printer is fine and the problem is with the first cartridge. If you have narrowed the problem to the toner cartridge, please carry out the following checks:

  • Confirm that you are using an original Lexmark brandtoner cartridge. If a third-party cartridge is causing this issue, please contact the point of purchase to have the cartridge replaced.
  • Confirm that the toner cartridge has not been refilled or reworked in any way. Refilling the toner cartridge can cause damage to the cartridge, leading to print quality issues of this kind. If the cartridge has been refilled or reworked, contact the place where the cartridge was refilled to have it replaced.
  • If this is an original Lexmark toner cartridge and it is relatively new or unused, it may be eligible for replacement. Contact the point of purchase first as they may have a replacement policy. If the cartridge was purchased directly from Lexmark, contact Lexmark using the phone number or address you used to order the cartridge. If the point of purchase cannot assist you or if you cannot remember or locate the number you used to contact Lexmark to order the cartridge, contact Lexmark Technical Support. A representative there may be able to provide more assistance.


If the issue occurs on more than one toner cartridge, continue with the suggestions below.

If the issue appears only on the first couple of pages/envelopes

If the issue is appearing only on the first couple of pages/envelopes printed after the printer is powered on, updating the printer's engine code may correct the issue.

Note:  Although this considered an "advanced" procedure, it can be performed by a customer. However, if you feel uncomfortable about carrying out this procedure by yourself or encounter any problems with it, please contact Lexmark Technical Support for additional assistance.



To check the printer's current engine code level, print out the Printing the Menu Settings Page.


On one of the pages, look for the header Device Information. Under Device Information, you will see Engine.


Check the printer's current engine code level. For example, if it says LS.ST.E204, the engine code level is 204.

  • If the engine code level is below E211 (e.g., LS.ST.E209), updating the engine code to the most recent level should correct this issue. Continue with step 4.
  • If the engine code level is at E211 or higher, skip past this table of steps and proceed to the section below labeled 'Check the charge roll assembly'.


To obtain the current engine code level:

  1. Go to

  2. Type your printer model in the “Enter Product Name” field and click GO OR click on the picture of the correct printer model shown.

  3. Locate the “Downloads” tab.

  4. Select the version of the Operating System.

  5. Click the link available under "Firmware".


Save the file(s) to a directory or folder of your choice. Make a note of the location.


Once you have downloaded the file(s), unzip any .ZIP files to extract the necessary engine code files and instructions.


You will need to copy the engine code file to the printer. The method to use depends on how your computer is connected to the printer. Refer to the instructions in the downloaded files.

Note:  If the downloaded files do not include any instructions, follow the appropriate link below under Firmware Flash Methods.


Once you have updated the printer's engine code, power the printer off for 30 seconds to one minute. Then power it back on and try printing again.

  • If the printer works correctly, continue using it but observe it closely over the next couple of days to see if the issue returns.
  • If updating the engine code does not clear the issue or if the issue occurs again at a later date, continue with the suggestions below.

Firmware Flash Methods

Firmware Flash MethodsInformation

Embedded Web Server (EWS) Recommended

Open a browser and enter the IP address of the printer. Select Settings >Update Firmware.

USB utility

xref_updating-the-printer-firmware-using-usbutil-or-usb-flash-utility-topic_xref for the detailed steps.

USB thumb drive

Updating printer or MFP firmware using a USB thumb or flash drive for the detailed steps.


Updating the printer firmware via FTP for the detailed steps.

Check the charge roll assembly



Power off the printer and remove the toner cartridge.


Look into the upper area of the printer where the cartridge was sitting. Located near the top of the printer you will see a twin set of small gray rollers. This is the charge roll assembly. It is highlighted by a yellow box in the image below. Note: You may need to close the lid a little in order for the charge roll assembly to come down into view.


Remove any paper or other debris you find stuck on the rollers.


If the roller surface appears dirty, take a clean, dry cloth and clean off any toner on the surface of these rollers. Do your best to make sure all of the roller surface is clean.

Note:  Try not to touch the charge rollers with your bare hands. The surface is susceptible to contamination, and a permanent mark could remain on the rollers.


Inspect the charge rollers for any damage. If any part is damaged, the charge roll assembly will need to be replaced.

For more information on arranging repair service, please contact Lexmark Technical Support or an authorized service center.


If the charge rollers appear fine or if you have tried cleaning them, try printing again. If the print does not clear up after printing 10 to 20 pages, continue with the suggestions below.

Check the type of paper/envelope

Before arranging service on the printer, check the type of paper or envelopes you are printing on. Specialty papers (like letterhead stock, textured paper/envelopes, label stock, and card stock) can lead to print quality issues like this..

  • If you are printing on paper, confirm that it is plain white copy paper.
  • If you are printing on envelopes, confirm that the envelopes are of a standard type and are not textured or heavy.

If not, try printing on plain copy paper or standard white envelopes before seeking service to the printer. Please try this even if the print media you are using has worked in the past to eliminate any special print media as part of the cause of the problem. Print 20 to 30 pages to give the background issue a chance to clear up.For more information on recommended print media, see the 'Understanding paper and specialty media guidelines' chapter in the printer's User's Guide

Audience: ‘LEXMARK PARTNER’ only below



Set the printer to print the Menu Settings pages. Printing the Menu Settings Page for instructions. Alternatively, you can have someone send a print job from a computer to the printer. Make sure the print job consists of two or more pages.


As soon as you see the first page begin to exit the printer, either open the upper front cover or power off the printer. This will stop the printer in mid-print.


Remove the toner cartridge. You should see the second page still in the printer, underneath where the toner cartridge was. The print on this area of the page has passed under the toner cartridge, but not yet through the fuser unit.


Examine the print on this section of the page to see if the toner haze is present.

Note:  Exercise care as the toner on the front of the page will easily rub off.

  • If the haze appears on the first page but not on the part of the second page still under the cartridge, the fuser unit is the likely cause of the issue.
  • If the toner haze appears on the second page, you can eliminate the fuser as a possible cause. The most likely causes of the issue are the charge roll assembly or the toner cartridge.


Once you have completed this test, remove all paper that is jammed in the printer. Again, use caution when removing the pages that did not feed through the fuser unit as the toner will come off.

  1. Charge roll assembly

  2. High voltage power supply (HVPS)

  3. Printhead/Laser cable assembly (check the condition of the cable in the printer first, if possible)

  4. Fuser assembly

  5. System board

  6. Printhead assembly


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