Kyocera Error C7990 — What It Means & How to Fix It
By Ryan Green · Updated August 2026 · Independent guide · PrinterCare USA LLC (not affiliated with any printer manufacturer)
The C7990 error on your Kyocera printer can halt your entire workflow without warning. This waste toner sensor error typically means either your waste toner box has reached capacity or the sensor itself has failed to detect the toner level correctly.
Waste toner is collected during the printing process as part of normal operation. When the sensor malfunctions or the box is genuinely full, your printer locks up to prevent damage to internal components. We will walk you through the legitimate fixes, from simple resets to component replacement, so you can get back to work.
How to fix it — step by step
- Power cycle your printer completely. Turn off your Kyocera printer using the power button on the front panel and wait for all lights to extinguish. Unplug the power cable from the wall outlet and wait for a full two minutes to allow the printer's internal memory to reset. Plug the power cable back in and turn the printer on, then test with a print job to see if the error has cleared.
- Access the waste toner container. Locate the waste toner box inside your Kyocera printer, usually found in the lower front or side panel depending on your model number. Open the access panel by pressing the release tab or button and gently slide out the waste toner container. Note the current fill level by looking at the transparent window on the side of the container if your model has one.
- Empty the waste toner box. If the waste toner container is visibly full or near capacity, remove it completely and hold it upright over a waste bin. Open the cap or release mechanism on the container and carefully empty the toner into the bin, working slowly to avoid clouds of toner dust. Seal the container and reinstall it into the printer, ensuring it clicks firmly into place.
- Reset the waste toner counter manually. Navigate to the printer's menu screen on the control panel and look for Settings or Administration options. Find the Consumables or Waste Toner Counter section and select Reset or Clear Counter. Follow the on-screen prompts to confirm the reset, then power the printer off and back on to complete the process.
- Check the sensor for physical obstruction. While the waste toner container is removed, visually inspect the sensor area inside the printer where the container sits. Look for any loose toner, dust buildup, or debris blocking the sensor lens or infrared beam. Use a soft, dry, lint-free cloth to gently clean the sensor area without applying pressure or liquid.
- Inspect the waste toner container sensor contacts. Examine both the contacts on the waste toner container and the corresponding contact points inside the printer where the container seats. If you see toner residue or discoloration on these contacts, carefully wipe them clean with a dry cloth. Reinstall the container and ensure it is fully seated so the contacts make proper electrical connection.
- Test with a diagnostic print. Print a configuration page or test page from your printer's menu to verify that the error no longer appears. If your printer has a web interface, you can also check the device status page by entering the printer's IP address into your browser on Windows 11 or macOS. Document any error codes that appear so you can reference them if professional support is needed.
- Contact Kyocera support or request remote diagnostics. If the C7990 error returns after completing the steps above, the waste toner sensor itself may have failed and requires replacement or the printer's logic board may need attention. Contact Kyocera's technical support line or request a remote diagnostics session, which typically costs around forty-nine dollars and can pinpoint whether the sensor or another component needs service. Many authorized Kyocera service partners can also schedule on-site replacement if your printer is under contract.
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Frequently asked questions
What exactly is waste toner and why does my printer collect it?
Waste toner is excess toner powder that is removed from the printer drum and fuser during the normal printing process. Every print job generates a small amount of waste toner that must be captured and stored in a separate container to keep the printer clean and prevent damage to internal components. When the waste toner box becomes full, the sensor triggers the C7990 error to tell you it is time to empty or replace the container.
Can I ignore the C7990 error and keep printing anyway?
No, you should not ignore this error as it is a safety mechanism designed to protect your printer. Continuing to print with a full waste toner container can overflow inside the machine, damaging the drum, fuser, and circuit boards. Kyocera printers will not allow printing when this error is active, so the only way forward is to address the underlying cause.
How often do I need to empty the waste toner container?
The frequency depends on your monthly print volume and the size of your waste toner container, but most offices empty it every three to six months. Light home users may only need to empty it once a year or less. Your printer will alert you with the C7990 error when the container is full, so you do not have to guess or maintain a separate schedule.
Is the waste toner sensor replaceable or is it a permanent part of the printer?
The waste toner sensor is a replaceable component in Kyocera printers, though it is not a user-serviceable part on most models. If the sensor fails after you have confirmed the container is empty and clean, you will need to contact an authorized technician or Kyocera support to order a replacement sensor and install it. The cost of the sensor and labor typically ranges from seventy-five dollars to one hundred fifty dollars depending on your printer model and your service agreement.