120C931dn

OKI C931dn error 120: Imaging Unit Fault

The OKI C931dn error 120 is a warning regarding communication between the main controller and one of the imaging units (drums). When my OKI C931dn shows error 120, it means a drum chip is not responding. This device is sensitive to correct consumible alignment.

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Common causes

  • 1Dirty or faulty drum chip.
  • 2Incorrect drum installation.
  • 3Drum end-of-life.
  • 4Drum rotation motor failure.

Solutions

Quick Diagnosis

If the display highlights a specific color, focus on that drum unit first.

Step-by-step Solution

  1. Power off completely.
  2. Open front panel and remove drums.
  3. Clean the chips with isopropyl alcohol.
  4. Reinstall ensuring a firm click.

Prevention and Maintenance

Avoid touching the photoconductor surface, as oils will damage it.

When to call a technician

If cleaning contacts fails, the drum's driving gear might be broken.

Device technical specs

  • Technology: Digital LED
  • Consumable: C931 Series toner and drums
  • Speed: 50 ppm
  • Resolution: ProQ1200
  • Connectivity: Gigabit Ethernet
  • Official drivers / firmware

Steps to follow

  1. 1

    Open panel

    Access the front drum area.

  2. 2

    Remove drum

    Check all 4 drums for dirt or blockage.

  3. 3

    Reinsert

    Clean electrical contacts and reinstall.

Frequently asked questions

The printer is having trouble detecting one of the imaging units.

No, this relates to the drum unit.

Genuine OKI C931 drum and toner.

Protect from direct sunlight and dust.