Lexmark / CS / CX 310 / 410 / 510 series

31.66 - The printer does not detect the imaging unit correctly.

The printer does not detect the imaging unit correctly.

This guide is scoped to the CS / CX 310 / 410 / 510 series family. Exact menu wording, cartridge naming, and service behavior can still vary by model variant and firmware.

Severity

Medium

Most likely cause

The imaging unit is not fully seated.

Can you keep using it?

Maybe after the first checks

Consumables involved

Imaging unit, Toner cartridge

Can you keep using it?

Can you keep using it?

Contact customer support if any of these apply

  • !31.66 repeats after reseating the imaging unit.
  • !The printer cannot clear the code after a clean restart.
If the printer still starts normally: Finish the first checks once, then stop if the same message repeats or the printer still cannot return to ready.

What to check first

Step-by-step checks

  1. 1

    Consumable check

    Power off the printer and remove then reinstall the toner cartridge and imaging unit.

    Start with the official recovery step before moving on to parts or deeper servicing.

  2. 2

    Safe first step

    Confirm the installed supplies are genuine Lexmark parts.

  3. 3

    Safe first step

    Check date, time, and firmware before retrying.

Background

What this message usually means

Lexmark uses 31.66 for a missing or unresponsive imaging unit. The official steps are to verify genuine supplies, reseat the toner cartridge and imaging unit, confirm date and time, and update firmware if needed.

Diagnosis

Likely causes

Most common

The imaging unit is not fully seated.

Common

A non-genuine or faulty imaging unit is not responding.

Possible

The printer needs a firmware or date/time refresh before the supply check clears.

Service

When service or replacement is more likely

  • -Lexmark treats this as a 31.6x imaging-unit fault rather than a paper jam.

See also

Related codes in this family

Explore more

More Lexmark printer families

Keep browsing

Where to go next

Source notes

Lexmark's 31.6x guidance treats 31.66 as a missing or unresponsive imaging unit and recommends reseating the supplies, checking date and time, and updating firmware if needed.

Built around official Lexmark support pages for the CS/CX 310/410/510 family. Code behavior can still vary slightly by exact model, installed options, and firmware generation.

Printer error codes can vary a little by firmware, region, and exact model variant. Use this guide as a family-level starting point and stop if the next step would require disassembly or service-mode changes.

Known family variants: CS310, CS410, CS510, CX310, CX410, CX510

Last reviewed: 2026-04-12

Reference: Open reference

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