HP error 55.xx (DC controller communication error)
55.xx is an internal communication error between the printer's formatter (the board that handles the print data) and the DC controller (the board that runs the print engine). 55.0 or 55.1 indicate a general communication failure, and codes such as 55.06 or 55.0601 identify a specific command or memory fault on the DC controller. The printer stops and usually asks for a power cycle.
What causes it
- Loose or poorly seated formatter board
- Damaged cable or connector between the formatter and DC controller
- Firmware bug or corrupted firmware
- Faulty DC controller or formatter board
- Electrical surge or static damage
How to fix it, in order
Work down the list and stop when the printer recovers. The steps are ordered from most likely and least invasive to last resort.
Power the printer off and on
Switch off, wait 30 seconds, and switch on. A single 55 error after a power dip can be a one-off. If it repeats, continue below.
Reseat the formatter board
Unplug the printer. On most LaserJets the formatter is in a cage on the back or side held by thumbscrews. Slide it out a few centimetres and push it firmly back in so the connector to the DC controller mates correctly. Do not remove it while the printer is powered.
Remove any accessories
Take out extra memory DIMMs, EIO or Jetdirect cards, hard disks and USB accessories, then test. A failing accessory can hold the bus and cause 55 errors.
Update or reload the firmware
If the printer reaches Ready, update to the latest firmware via the embedded web server or an .rfu file sent over USB. HP's release notes list several 55.xx fixes for specific models.
Inspect the cable between the boards
On models with a flat cable between the formatter cage and the engine, check for a crushed or disconnected cable and reseat both ends.
Replace the DC controller or formatter
If reseating and firmware do not help, one of the two boards has failed. The error sub-code and the service manual identify which to replace first; typically 55.0x points to the DC controller.
Stopping it happening again
When it is not worth fixing yourself
If you would rather not work through this alone, a printer specialist can take a look with you on a screen-share and tell you honestly whether the machine is worth saving.
Frequently asked questions
What does 55.0601 mean?
It is a DC controller memory or command error on newer LaserJet Pro and Enterprise models. HP's guidance is to power cycle, update firmware, and if it persists replace the DC controller.
Is a 55 error caused by the network?
No. It is internal communication inside the printer between two circuit boards. The network interface is not involved.
Can a loose formatter really cause this?
Yes. The formatter plugs directly into the DC controller on most LaserJets and a partial connection produces exactly this error. Reseating it fixes a surprising number of cases.
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