Can you keep using it?
Can you keep using it?
Contact customer support if any of these apply
- !The duplex jam returns on clean paper after a full path clear.
- !The duplex latch or guide no longer seats correctly.
What to check first
Step-by-step checks
- 1
Consumable check
Open the front door, remove the imaging unit if required, and clear visible paper.
Start with the official recovery step before moving on to parts or deeper servicing.
- 2
Safe first step
Open the duplex unit and remove any jammed sheets or scraps.
- 3
Consumable check
Retry with flatter paper or one-sided printing if duplex jobs keep failing.
Background
What this message usually means
Lexmark's MX431 office guide treats duplex-unit jams as a separate rear-path problem that needs the imaging unit area and duplex unit checked together. It usually means the sheet failed during two-sided handling and did not reverse cleanly through the duplex route.
Before the message
What users usually notice first
Messages like this often appear after a hidden paper-path interruption, tray setup issue, or a small obstruction that is easier to miss than a full visible jam.
Diagnosis
Likely causes
Paper stalled in the duplex path during two-sided printing.
A torn scrap remains in the duplex route.
Curled or unsuitable media failed during duplex reversal.
Service
When service or replacement is more likely
- -If only duplex jobs fail, the main print engine may still be fine and the reverse path is the likely problem.
Avoid wrong turns
Common misreads of this message
- -Treating the message like a confirmed failed part instead of a support clue about which system has stopped the printer.
- -Assuming no physical path issue exists just because no full sheet is visible at first glance.
See also
Related codes in this family
Explore more
More Lexmark printer families
Read this next
Helpful guides for this problem
Boundary
When to stop troubleshooting and move to support
Use the message once to classify the problem, then move to support if the printer still cannot return to ready after the first safe checks.
Keep browsing
Where to go next
Source notes
Lexmark's official duplex-unit jam guide for the MX431 family walks through opening the front door, removing the imaging unit, and clearing the duplex path.
Built around official Lexmark user-guide and service-manual material for the MX431 and closely related mono office models. Exact code behavior can vary a little by print-only versus MFP model and installed options, but the main paper-jam and supply messages stay close across the family.
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: MX431adn, MX431adw, MS431dn, MS431dw, XM1342
Last reviewed: 2026-04-12
Reference: Open reference