u1-2120Phaser 3155

Error U1-2120 Xerox Phaser 3155: Registration Fault

The Xerox Phaser 3155 error U1-2120 is a paper synchronization alert, specifically in the registration area just before entering the drum. Users often ask: why does my Xerox Phaser 3155 show error U1-2120? after attempting to print multiple sheets continuously, which often overloads the traction roller. This fault is fundamentally mechanical and requires an inspection of the paper presence sensor actuators.

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Common causes

  • 1Registration sensor obstructed by toner dust or paper.
  • 2Premature wear of the pickup roller causing slippage.
  • 3Physical obstruction by invisible paper scraps behind the drum.
  • 4Paper sensor actuator jammed by sticky residue.

Solutions

Quick Diagnosis

The U1-2120 error is distinguished by occurring just as the paper begins to enter the printing zone. If you hear the motor turning but the paper does not advance toward the fuser, it is almost certain that the registration sensor is blocked or traction is insufficient.

Step-by-step Solution

  1. Open the rear unit of the printer and verify there are no paper remnants blocking the path.
  2. Clean the registration sensor actuator (a small plastic lever) with compressed air or a dry cloth.
  3. Ensure the paper guides in the tray are not too tight, which would cause resistance.
  4. Close everything and reset the system to test loading again.

Prevention and Maintenance

To prevent error U1-2120, keep the interior of the printer free of paper and toner debris, which can impede sensor movement. Use standard quality paper to avoid traction deformations. Cleaning the feed rollers with a dry cloth periodically ensures that the paper has the necessary grip to reach the registration sensor on time.

When to Call a Technician

If you have cleaned the sensor and verified the path, but the motor still makes an abnormal noise when trying to load paper, it is likely that the traction unit or motor clutch needs professional maintenance or replacement.

Technical Data

  • Technology: Monochrome Laser Printer.
  • Performance: 23 ppm.
  • Connectivity: USB.
  • Feeding Capacity: 250-sheet tray.
  • Compatible Consumables: Xerox 106R01485 Cartridge.
  • Recommended Use: Home and small offices.
  • Official Drivers / Firmware

Steps to follow

  1. 1

    Check path

    Open the rear unit and verify that there are no paper scraps obstructing the registration sensor.

  2. 2

    Clean actuator

    Clean the registration sensor actuator using compressed air to remove toner dust.

  3. 3

    System reset

    Close all covers and power on the equipment to initialize the traction system.

Frequently asked questions

The U1-2120 occurs when a sheet of paper takes longer than expected to reach the registration sensor after moving through the feed roller.

It is not complex; most often the sensor is just jammed or dirty from heavy use.

A worn cartridge can release toner that sticks to sensors, causing incorrect readings.

We recommend cleaning the rollers every 20,000 prints or if you notice paper slipping during loading.