HP Color LaserJet 4600dn Cyan cartridge "not installed" error after black laser scanner repair

[ManiacCoder]

I just repaired the laser scanner corresponding to the black cartridge in my HP Color LaserJet 4600dn printer to fix the 51.2K error message (shout out to community member Davidzuts for his spot-on comment on this repair). I put everything back together and fired up the printer and it now gives me the message "Install Cyan print cartridge". The odd thing is that (using diagnostics mode) I can print out the supplies information and can see that the printer detects the cartridge (it reads the serial # and usage) but it can't/wont print cyan. I've tried turning off cartridge detection, which allowed me to print test pages as well as swap cartridges (I swapped black and cyan, same error). I also had the old Cyan cartridge (which is an original HP cartridge) and still get the same error. Based on my testing, the problem is with the cyan (lowest) cartridge slot and not with the actual cartridge itself.

The 51.2K error is completely fixed but now I have this new dilemma and am not sure where to start looking. I'm hoping that someone on the board has some good advice on things to check/places to look to determine the root cause here as I'm really at a loss and am hoping to save this printer from the landfill.

When I power on the printer, it goes through all of it's checks and then I see the "Ready" screen for 2-4 seconds, after which the "Install Cyan Cartridge" message shows up. It's got to be related to something that I did (or didn't) do during the laser scanner fix but I'm at my wits end to figure out what.

[Repairatrooper · Accepted solution]

Go  back and check all the wiring. Trace the cable back from the sensor to the main board to ensure it is connected. You likely removed quite a few components to access the scanners and the wiring can be a spider web.

[ManiacCoder]

I went back through the printer this morning and the issue appears to have been that the cyan laser scanner shutter arm did not get correctly positioned on the piece that lifts it open. This is as best as I could tell at least -- when I got back into the cabinet where the laser scanners were located and removed the retention bars, the only thing that I could see different for the cyan vs. the others was the shutter arm on the 3 other scanners was on top of the black lift part while the cyan appeared to be in front of/pushed into it.

The wiring was all good and everything else other than the above appeared to be fine. Taking extra care to seat the cyan laser scanner the same as the others and then putting it all back together seems to have done the trick and I now have a working printer again! This makes me very happy since, while it is an old printer, it really hasn't had that many pages run through it and I expect (hope/fingers crossed) that it will last many, many more years - or at least as long as I can milk it out!

For others that might be adjusting/replacing a laser scanner for the first time, while HP has done a very nice engineering job to make this process relatively easy, it still pays to give extra attention to how the scanners go back into the cabinet. When I reassembled it the first time, everything looked great but as I discovered, just a little thing threw the entire printer off.