How to Fix Epson ET-8550 Scanner Error 100016 - Causes and Solutions

Question:
I have an Epson ET-8550 printer, and whenever I try to scan, the pulley moves slightly and then stops with the error 100016. What could be causing this, and how can I fix it?

Answer:

Now, let's discuss the Epson Error 100016 you're experiencing. This error commonly appears when the scanner unit motor or its related components encounter resistance or communication failure. In the Epson ET-8550 and similar models, this system uses a stepper motor, a pulley-and-belt mechanism, and a position scale (or encoder strip) to move the scanner head smoothly. If the printer detects that the scanner head cannot move freely or that the motor rotation signal is inconsistent, it stops and displays the 100016 error.

Here are the most likely causes and corresponding fixes:

1. Scanner Motor Failure or Stall:
   The small motor that drives the scanner assembly might have failed or become obstructed. Try listening closely when you power on the printer-if you hear a weak hum or short movement followed by a stop, the motor could be under strain or burned out. In many cases, replacing the scanner motor assembly resolves the issue.

2. Contaminated or Damaged Encoder Scale:
   The clear plastic strip or thin metallic scale along the scanner's travel path helps the printer track position. Dust, ink mist, or fingerprints on this strip can confuse the optical sensor, triggering Error 100016. Gently clean it using a lint-free cloth slightly dampened with isopropyl alcohol. Do not use excessive pressure, as the strip is fragile.

3. Blocked or Misaligned Scan Carriage:
   Sometimes the scanner carriage gets jammed due to small debris, excess lubricant, or a warped guide rail. Open the scanner lid and inspect the track. If the carriage doesn't slide smoothly by hand (with the printer turned off), clean the rail and check for mechanical interference.

4. Broken Pulley or Drive Belt:
   Since you noticed that the pulley moves only slightly, inspect the drive belt connecting the pulley and the scanner motor. A partially detached or stripped belt can prevent the carriage from completing its travel, leading to the 100016 error. Replace the belt if it's loose or frayed.

5. Firmware or Sensor Communication Error:
   Although rare, firmware issues or sensor misreads can also cause false 100016 errors. Try unplugging the printer for at least five minutes, then power it back on to allow the internal sensors to reset. If the problem persists, updating the printer's firmware from Epson's support site may help.

If you've verified that the carriage moves freely, the belt is intact, and the motor can spin when nudged, then the scanner motor sensor (often referred to as the scale sensor) could be defective. Unfortunately, this component isn't user-serviceable and typically requires replacement of the scanner assembly or the entire unit.

Addressing printer and scanner problems can be a complicated affair due to their hands-on nature. So, we're not able to provide remote troubleshooting, suggestions, or support for printer repairs. We do, however, offer an in-person evaluation and repair service via our local diagnostic facility (https://bchtechnologies.com/printer-repair-service). Given the high demand, we operate on a first-come, first-served basis, and it may take a few weeks before we can inspect your printer. Our repair services cover both full printer restoration and part-specific fixes, with clear guidance provided on how to proceed. While our rates may not always be the lowest, we highly encourage self-help if possible. You can start by researching related repair techniques on YouTube-especially through our BCH Technologies channel (https://youtube.com/@bchtechnologies). Use the search icon near the "About" section to find videos by model or error code.

Thank you again for your patience and for being part of the BCH Technologies community. Your curiosity and feedback inspire us to keep sharing detailed, hands-on solutions for printer and scanner repairs.