u4fi-5900C

Fujitsu fi-5900C Error U4: Sensor Fault

Fujitsu fi-5900C scanner error U4 flags a document detection sensor failure. Unlike paper jams, this error occurs because the optical sensor logic detects an anomaly (either stuck paper presence or failed light transmission). Troubleshooting the Fujitsu fi-5900C error U4 involves deep cleaning of sensor pathways.

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Common causes

  • 1Sensor dust accumulation.
  • 2Optical sensor failure.
  • 3Mechanical object blocking light path.
  • 4Defective sensor logic board.

Solutions

Quick Diagnosis

If the error code U4 appears without paper in the tray, a sensor has likely accumulated enough dust to think there's a permanent paper feed.

Step-by-step solution

  1. Turn off the power and open the main scanner cover.
  2. Locate the paper path sensors (usually small plastic tabs or LED pairs).
  3. Carefully clean the sensors with dry compressed air.
  4. Close the scanner and power it back up to allow a sensor reset.

Prevention and maintenance

Routine cleanings using the recommended kit are vital for industrial scanners. Do not use liquids directly on the optical sensors.

When to call a technician

If the U4 error persists despite thorough cleaning, the internal sensor board might be dead.

Equipment data

  • Technology: Industrial Scanner
  • Speed: 100 ppm
  • Connectivity: USB / SCSI
  • Compatible Consumables: Roller / Pad Kit
  • Capacity: 500 sheets
  • Usage: Industrial
  • Official Drivers

Steps to follow

  1. 1

    Clean optical sensors

    Use a clean swab to gently remove dust from paper detection sensors.

  2. 2

    Cycle the scanner lid

    Open and close the covers to ensure all mechanical sensors engage.

  3. 3

    Reboot

    Restart the scanner to re-calibrate detection sensors.

Frequently asked questions

It typically signals a paper detection sensor that is dirty or permanently blocked.

Clean the paper path monthly and avoid dusty documents.

No, but regular cleaning of roller pads helps reduce debris falling onto the sensors.

If sensor cleaning fails, the LED sensor component may be burnt out.

Fujitsu fi-5900C Error U4: Sensor Fault | Vimazdev