Magenta (yellow) unit is PAST end of life... (I have changed cartridges I still have this message. I tried to read instruction, and I got following message: Install P/N 108R00649 following the instalation)

If the message Change Imaging Unit Magenta displayed refer to imaging unit with contents a developer.The Imaging unit life is 80.000 copies.
The imaging units located after front door when is located the waste toner box.
If the message M toner end/change the M toner displayed refer to toner cartridge
The toner cartridge life 15.000 copies 5% saturation.In full color mode the color saturation is 80% and the color toner life is 6.000-8.000 copies.
I think your problems is a toner not the developer.

Remove the magenta cartridge then re-install the yellow followed by the magenta

I have a similar problem now: magenta stain over the entire page when printing anything with any color (even just a hyperlink); B&W text is no problem.Not the PC; even the Demo Page from the 4040 menu does this. Updated the 4040 firmware tonight to latest (1.24, etc), but no better.Recently replaced the Magenta cartridge (official Brother cartridge), though saw this problem near end-of-life of the previous Magenta cartridge. Drum Unit status is 42%, so not expected to be near end-of-life.

it shows that yellow and magenta colors gone end, need re-fill or replacement.
hope it helped, if so rate the solution

There's a window on each end of the cartridges and light shines thru to show when they're empty, your refill toner may not be the right density. If you put a small piece of electrical tape over the windows on the cartridge, the error will go away, but you have to watch print quality to change or add toner.

To reset the sensor after installing a new toner cartridge follow these steps.
1. With unit powered On, open the front cover.
2. Press the "Options" key. Display will show "Replace Drum?"
3. Press "Start" key.
4. Press 1,0 .
5. Display will show "Accepted" for approximately 2 seconds. Then display will change to "Cover Open".
6. Close cover and see if Toner Life End error message has gone.
Please note that this must be done with a new cartridge so the unit will see that there is toner in the cartridge.

This happened to me twice, You can possibly have no ink in your cyan,magenta and yellow , you would then have to replace them to work the set. I had to do that and it worked =]

Hi rmcday: Here your problem. The imaging unit creates the image using an electro-photo process. The imaging unit consists of the following: ■ An OPC Drum ■ Waste Toner Assembly ■ Charge Roller Assembly 9.0 Consumables, Routine Maintenance Items and Options Item Life based on 5% coverage Part No. Replaceable by Black Standard Toner Cartridge Black High capacity 3,000 7,000 106R00679 106R00684 User replaceable Cyan Standard Toner Cartridge Cyan High capacity 2,000 5,000 106R00676 106R00680 User replaceable Yellow Standard Toner Cartridge Yellow High capacity 2,000 5,000 106R00678 106R00682 User replaceable Magenta Standard Toner Cartridge Magenta High capacity 2,000 5,000 106R00677 106R00681 User replaceable Imaging Unit 50,000 images 108R00593 User replaceable Transfer Belt 50,000 images 108R00594 User replaceable 500-Sheet Feeder N/A 119650600 Waste Toner Cartridge 3,000 to 5,000 pages (color 5%) 106R00683 User replaceable. Your imaging unit may have exeeded it life of 50,000 pages and will need to be replaced. Hope this helps

The warning is for the photo conductor units, these are the four units that sit on the transfer belt. If you open the front cover you will see these units sitting on the inside of it when you pull it down. Normally when this message display, not long afterwards the print quality will start to suffer. From experience it's best to replace all four units together, because when one goes the rest seem to follow suit!

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HP Color LaserJet 2600n Printer - Installing Print Cartridges When a print cartridge approaches the end of useful life, the control panel displays a message recommending that to order a replacement. The printer can continue to print using the current print cartridge until the control panel displays a message instructing to replace the cartridge. The printer uses four colors and has a different print cartridge for each color: black (K), cyan (C), magenta (M), and yellow (Y). Replace a print cartridge when the printer control panel displays one of the following messages: Replace yellow cartridge, Replace magenta cartridge, Replace cyan cartridge, Replace black cartridge. The control panel display also indicates the color that should be replaced (unless a genuine HP cartridge is not currently installed). Change the print cartridge

1. Turn off the printer.
2. Open the front door. CAUTION: Do not place anything on the transfer belt (ETB), which is located on the inside of the front door.
3. Remove the used print cartridge from the printer.
4. Remove the new print cartridge from the bag. Place the used print cartridge in the bag for recycling.
5. Grasp both sides of the print cartridge by the blue handles and distribute the toner by gently rocking the print cartridge from front to back. CAUTION: Do not touch the shutter or the surface of the roller.
6. Remove the orange shipping locks and the orange shipping tape from the new print cartridge. Discard the shipping tape and shipping locks according to local regulations.
7. Align the print cartridge with the tracks inside the printer, and using the handles, insert the print cartridge until it is firmly seated.
8. Firmly close the front door.
9. Turn on the printer. After a short time, the control panel should display Ready.
   NOTE: If a cartridge is in the wrong slot or is the wrong type for the printer, the control panel will display one of the following messages: Incorrect yellow, Incorrect magenta, Incorrect cyan, Incorrect black.
10. Installation is complete. Place the used print cartridge in the box in which the new cartridge arrived. See the enclosed recycling guide for recycling instructions.
11. If a non-HP print cartridge is in the printer, check the printer control panel for further instructions.
    NOTE: When replacing or changing a black print cartridge, a cleaning page will automatically print. This helps prevent speckles on the front or back of printed documents. A cleaning page can also be generated using the control panel or the HP Toolbox.