Samsung ML-451 Series Service Manual page 210

4. Alignment and Troubleshooting
► Error Code
U1–2117
► Error message
Fuser Unit Failure #U1-2117 : Turn off then on.
► Symptom
The machine can't detect that the fuser unit is installed.
► Troubleshooting method
1) After checking the fuser installation, turn the machine off then on.
2) Open the rear cover. Lift up the right side and release the rear cover.
3) If there is no problem, remove 4 screws.
4) Lift up the both levers. Then take off the fuser unit.
4-109 Copyright© 1995-2016 SAMSUNG. All rights reserved.