391es4131dn

OKI ES4131dn Error 391: Toner Not Detected

The OKI ES4131dn error 391 is a critical message meaning that the printer cannot communicate electronically with the toner cartridge chip. This prevents the device from verifying the consumable level, its authenticity, or its compatibility, blocking printing to avoid quality errors or imaging unit damage.

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Common causes

  • 1Dirty or damaged contact on toner chip.
  • 2Packaging tape blocking the electrical contact.
  • 3Generic cartridge with faulty chip.
  • 4Printer's internal connector out of alignment.

Solutions

Diagnostic quick-check

If you recently changed the cartridge and the 391 error appeared, the problem is almost certainly a physical chip connection. If the toner was already installed and suddenly started failing, there might be accumulated dirt on the cartridge terminals.

Step-by-step solution

  1. Open the front cover and remove the cartridge.
  2. Examine the small square chip on the side of the toner.
  3. Clean the chip carefully using a soft eraser; wipe away any residue afterwards.
  4. Verify that no orange security tape is blocking the contact.
  5. Reinstall the toner and close the cover; wait for the printer to complete the detection cycle.

Prevention and maintenance

Handle consumables with care. Avoid touching chips with fingers to prevent skin oil transfer, which can oxidize contacts over time.

When to call a technician

Call if you have tested several compatible/original cartridges and none are detected, as this suggests a break in the printer's internal board connector.

Device technical sheet

  • Technology: LED laser printer.
  • Speed: High productivity.
  • Connectivity: USB and network.
  • Compatible consumable: ES4131 Toner.
  • Recommended use: High-volume offices.
  • Official drivers / firmware

Steps to follow

  1. 1

    Reinstall toner

    Remove the cartridge and re-insert it, checking that it clicks into place.

  2. 2

    Clean contacts

    Clean the metal contacts on the cartridge chip with a soft pencil eraser.

  3. 3

    Physical check

    Check that the toner locking levers are not damaged.

Frequently asked questions

The 391 indicates that the printer cannot read the electronic chip of the toner, preventing its use.

It often happens with third-party toners that have low-quality or poorly positioned chips.

Check that you have removed all orange safety tapes before installing it.

It is rare, but if you have tested several cartridges and all give an error, it is a failure of the printer's internal contacts.