What this means

Your printer has stopped because the waste toner container is full or sitting incorrectly. This box catches the excess toner left over from normal printing and calibration. When the internal sensor detects that it is full, the machine locks up.

You might think this means a broken sensor or a complex internal failure. Usually, the box is simply full and needs replacement. If the box is new or actually empty, the error means the unit is not seated properly.

Reseating the box triggers the sensor to clear the error. Genuine boxes use specific latch mechanisms to click into place. Never reuse an emptied container. Doing so causes sensor failures and leaks toner inside your machine.

Common causes

  • The waste toner box is full of toner waste.
  • The waste toner container is loose or improperly installed.
  • Toner sensor is obscured by debris.
  • Damaged locking latch on the waste toner box.
  • An attempt was made to reuse an old waste toner box instead of replacing it.

What to check first

  1. 1Check the front or side door of the printer to locate the waste toner container.
  2. 2Verify that the printer has completely stopped its mechanical operations before opening any doors.

Step-by-step fix

  1. 1

    Open the waste toner access door

    Open the designated cover on the printer to access the waste toner box.

  2. 2

    Remove the waste toner container

    Press the release levers if applicable and gently pull the waste toner container straight out of the printer.

    Keep the container upright to avoid spilling toner powder.

  3. 3

    Check and clean the area

    Inspect the cavity where the waste toner box sits for any loose toner or obstruction.

  4. 4

    Install a new waste toner container

    Insert a fresh, unused waste toner container firmly into the slot until it clicks into place.

  5. 5

    Reseat the container if needed

    If the container was recently replaced, remove it and reinsert it to ensure the connector engages properly.

  6. 6

    Close the access door

    Close all printer covers securely and check if the error code clears from the display.

When to contact a professional

Call a technician if a genuine waste toner container does not clear the C7990 error. Call for help if the internal sensor connector is broken. Do not attempt to fix broken internal parts yourself. Toner dust is an inhalation hazard. Never reuse an old waste toner container.