This article is in regards to the issue of continuous calibration in the HP Color Laser Jet 3600 series printers.
Other models affected are
Color Laser Jet 3000, 3600, 3800 printers.
Problem: Continuous Calibration

Calibrating and the Electrostatic transfer belt (ETB)
When your printer calibrates, it is checking for a toner patch that is laid on the ETB or transfer belt assembly. It is also adjusting the location or registration of where each color is laid.
If you change one of the toner cartridges or the transfer belt it will automatically calibrate itself. It will sound like it is making a copy and you will see Calibrating on the display. With this calibration issue the problem is that it will never stop calibrating or come to ready.
You can calibrate it yourself.
Calibrating the printer
Calibration is a printer function that optimizes print quality. If you experience any print-quality problems, calibrate the printer.
1. Press Menu.
2. Press to highlight CONFIGURE DEVICE, and then press .
3. Press to highlight PRINT QUALITY, and then press .
4. Press to highlight FULL CALIBRATE NOW, and then press .
When the machine begins calibrating it looks for a patch of toner on the ETB. If it doesn’t sense it or if the patch is light the machine will not complete the calibration.

Color Registration
The calibration also takes sensor readings with the color mis-registration sensor. It checks each color and adjusts them so that they are aligned. If the printer didn’t calibrate and align the colors the machine wouldn’t know where to lay down each color and your image would be offset, blurry and just not good.
Trouble-shooting Steps
Inspect each toner cartridge and make sure that the pull seal strip is removed. Make sure that the pull tape didn’t break off inside. If you believe it may have broken off inside you should replace the toner cartridge. You should be able to get credit for the cartridge as defective.

Testing the Toner Cartridges
You can let it begin calibrating then stop it by opening the front door, Look on the ETB. You should have all four colors laid on the belt. If each toner cartridge is working correctly it will be laid on the belt. If you can see it but it is much lighter than the others or its not present there is a problem. See image below

It is possible that the ETB may have an issue such as a bad sensor, so you may have to replace the ETB. I would trouble shoot with the hopes that this is not the issue, but it could be the case. There is a way to bypass the calibration and get it to come to ready though the print quality may be horrible. If you are out of ideas it can’t hurt to try this.
To Skip Calibration
1. Turn the printer off and then on.
2. When the printer begins its initialization sequence, press and hold the “DOWN” arrow until all LEDs are lit.
3. Press the “UP” arrow one time, and then press “Menu”.
4. Press the “UP” or “DOWN” arrow until it comes to “Skip Calibration”.
5. Press “CHECK”.
NOTE: Do not press check when it is displaying “NVRAM INIT”!
The problem for me has always been a bad toner cartridge or a toner cartridge with the seal left in it. It really is a tricky problem for even a technician so I wish you luck. I believe that this problem has to be a firmware issue and I don’t believe HP will ever fix it. It is such an old printer at this point it would be senseless to spend the money and yet there are many people that still have these printers.