OKI Error Error 173 — What It Means & How to Fix It
By Ryan Green · Updated August 2026 · Independent guide · PrinterCare USA LLC (not affiliated with any printer manufacturer)
Error 173 on OKI printers is one of the most common hardware failures you'll encounter, and it's frustrating because it stops your entire workflow instantly. This error specifically indicates that the fuser unit—the heating component that permanently bonds toner to paper—has detected a temperature sensor failure, thermal runaway condition, or internal electrical fault.
The good news is that Error 173 has predictable causes and straightforward solutions. In many cases, a simple power reset resolves the issue within minutes. If it doesn't, you're looking at either a replaceable thermal fuse, a failed temperature sensor, or ultimately a fuser unit replacement, which typically costs between seventy and one hundred fifty dollars in parts depending on your OKI model.
How to fix it — step by step
- Power cycle the printer completely. Unplug the power cable from the back of your OKI printer and wait for exactly two minutes. This allows the fuser unit's thermal components to cool completely and resets any temporary sensor errors. Plug the printer back in, wait for the startup sequence to finish, and check whether Error 173 has cleared from the display.
- Check for visible debris in the fuser area. Open the rear access panel of your printer by locating the release latch on the left side. Visually inspect the fuser unit assembly for torn toner residue, paper fragments, or foreign objects lodged near the heating element. If you see debris, use a dry, lint-free cloth to gently wipe the exterior of the fuser cartridge only—do not attempt to disassemble the unit.
- Verify the fuser unit is seated correctly. Locate the fuser cartridge in the rear section of the printer. Grasp the green or blue handle on the fuser unit and gently pull it straight out about one inch, then firmly push it back in until you hear or feel it click into place. This reseats the electrical connector and can resolve intermittent sensor communication errors.
- Replace the thermal fuse if accessible on your model. Some OKI models have a user-replaceable thermal fuse located on the fuser power supply board. Consult your specific model's service manual to confirm whether this fuse is accessible without full disassembly. If accessible, locate the fuse labeled T-Fuse or similar, note its amp rating, and replace it with an identical part from an electronics supply store for under five dollars.
- Clean the fuser unit temperature sensor. The fuser unit contains a thermistor or temperature sensor that can become contaminated with toner dust over time. If you're comfortable opening the fuser access door, use a clean, dry cotton swab to gently wipe the small sensor element, which is typically a small metal probe or ceramic component. Do not use liquids or apply excessive force.
- Reset the printer to factory settings. Navigate to the printer's menu using the control panel buttons and locate the Reset or Maintenance menu. Select Reset to factory settings or Clear all errors if available. This clears persistent error flags that may be incorrectly triggering Error 173. Allow the printer thirty seconds to reboot.
- Update the printer firmware. Visit the OKI support website and search for your exact printer model number. Download the latest firmware update file to your Windows or Mac computer, then follow the provided instructions to upload it to your printer via USB or network connection. Firmware updates sometimes address sensor calibration issues that cause false Error 173 readings.
- Order a replacement fuser unit if errors persist. If Error 173 continues after all troubleshooting steps, the fuser unit's heating element or internal circuits have failed permanently. Contact an authorized OKI supplier with your model number to order a replacement fuser unit assembly, or book a technician service call. Remote support is available for $49 if you prefer guided assistance with any of these steps.
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Frequently asked questions
Will Error 173 go away on its own or do I absolutely have to fix it?
Error 173 will not resolve without intervention because it indicates a genuine hardware fault in the fuser unit. Your printer will remain locked in an error state and refuse to print jobs. However, the power cycle step fixes approximately forty percent of Error 173 cases, so always start there before assuming you need parts.
Can I just replace the toner cartridge instead of dealing with the fuser unit?
No, the toner cartridge and fuser unit are completely separate components. Error 173 specifically indicates a fuser unit problem, not a toner issue. Replacing the toner will not resolve this error, though it's worth checking that your toner cartridge is not defective as a secondary step.
How much does it cost to have someone professionally replace the fuser unit?
A professional fuser unit replacement typically costs between one hundred twenty and two hundred fifty dollars total, including parts and labor depending on your location and printer model. If you prefer to do it yourself, the fuser cartridge alone costs seventy to one hundred fifty dollars, and the replacement process takes approximately twenty to thirty minutes with proper guidance.
Is Error 173 covered under my printer's warranty?
Fuser unit failures are covered under the manufacturer's warranty for the first year from purchase date. If your printer is still within warranty, contact OKI customer support or your authorized reseller with your model number and purchase documentation to arrange a free replacement or repair. If your warranty has expired, you'll need to pay for repair or replacement.