HP 4600 has magenta and cyan marks on back of printouts.

Yellow ATC Sensor Failure,Code12
Magenta ATC Sensor Failure,Code13
Cyan ATC Sensor Failure,Code14
The ATC Sensor detects an insufficient amount of developer.

Note
If this failure reoccurs three times successively, an Engine NVRAM value is set preventing further printer use until the Clear Tech Rep Fault (see pg.6-20) is performed.

Troubleshooting Procedure
Step Actions and Questions Yes No 1 Is the problem toner and/or developer empty. Replace the toner or developer. Go to step 2. 2 Is the ATC sensor clean and free of dust, toner or any other contaminates? Go to step3. Clean the ATC sensor. 3 1.Check the ATC sensor wiring harness Yellow=P/J129
Magenta=P/J130 Cyan=P/J131
2.Is the wiring harness or the sensor defective? Replace the ATC Sensor and/or wiring harness. Go to step 4. 4 1.Remove the Rear Cover and RearShield.
2.Measure the voltage at...Yellow=P405B3 Magenta=P405B8 Cyan=P405A10
on the engine control board.
3.Is the voltage between+1 and
+3VDC? Replace the engine control board. Go to step 5. 5 1.Measure the voltage at...Yellow=P405B14 Magenta=P405B11 Cyan=P405A11
on the engine control board.
2.Is the voltage+5VDC? Replace the engine control board. Go to step 6. 6
1.Measure the voltage at...Yellow=P405B2 Magenta=P405B9 Cyan=P405A9
on the engine control board.
2.Is the voltage 0VDC? Replace the engine control board.
Go to step7.
7
1.Remove the Imaging Unit Plate cover.
2.Inspect the wiring harness between the engine control board and the developer housing assembly.
3.Is the wiring harness defective? Replace the wiring harness.
Replace the ATC Sensor.
8
Run approximately 10 pages of the solid fill full-page prints for this color to ensure the error is cleared.

Since you have Cyan toner in places where it should not be then the only possible cause is a defective Cyan Toner cartridge. I worked on one just last week where the customer complained about Magenta toner on their prints. I also noticed Magenta toner on the Transfer Belt just as you see Cyan toner on the Transfer Belt. I replaced the Magenta Toner Cartridge and everything cleared up nicely. The Transfer Belt Unit can also cause similar problems but it would not be ONLY one color like Cyan. It would be a mixture of all colors. My bet is replace the Cyan toner and you will be fine. If you have an old empty one just shake it up a bit and try it as well. This might allow you to verify before buying a new cartridge.
Good Luck and Thank You for using Fixya.
Wheatland Services

Dirty laser unit - needs (careful) cleaning internally.

See ' Printing Weak Magenta', 'Printing Light Magenta' for HP CM1015, HP Color Laserjet 1600, 2600, 2605.

All the same laser unit

Dear this printer is solve this problem just

chnge the magenta toner scaner ok ........after that is working but ...do not any idea about this just call me :+91-09328015664
and Email:[email protected]

your printer's gear box time seting is not in its place so you dont have the right colors

51.22 is a Magenta laser scanner error.
Try removing the magenta restarting the printer and reinstalling.
If that does not work you likely need a laser assm.
You might want to call a tech. to replace.

At a guess you are using recycled toners? If the recycler has not worked out the refilling procedure properly, the problem you experienced with the exploding Cyan toner is common. It is possible in the act of blowing out the loose cyan toner your have used to much air pressure, possibly blowing toner into the laser beam units, or damaging the toner sensor unit for magenta.
A diagnostic inspection, by a technician would be suggested.
Cheers: DeJudge

Firstoff, if you have tray 1 set to "any size" & "any type" they had problems with it going into calibration to frequently. If you upgrade the firmware this will take care of that. As for no Cyan, check the scanner interlock to insure it is opening the scanner cover. You could also go into diagnostics and disable cartridge check and swap the cartridges around, ie. cyan & magenta, run the print quality pages and see if the problem follows the cartridge. It could also be HV power supply.

I had the same problem and found that one of the toner cartridges must have not been seated properly. I removed the black toner cartridge and re-fitted it. The printer now works fine again with no errors. 17H is a code relating to a fault in the rotation ......... possibly one or more toner cartridges need checking. Use the menu on the printer to turn it to the appropriate position (i.e. engine menu then select replacement of whichever toner you are checking).
Hope this fixes your as well.
Chris

there should be a light flashing on the printer. try pressing the button nearest to it to see if that will move the print head out in order that you can replace the cartridge