Epson Scanner Error 100016: Should the Gears Turn Manually, and How Can You Identify the Cause?

Question

I watched your video, How to Fix Error 100016 on Your Epson Scanner [https://www.youtube.com/watch?v=4dZ9YM6aFDU], and isolated the problem to the scanner mechanism. Should I be able to turn the scanner gears manually while the printer is switched off?

I have tried realigning the gears, but when I turn on the printer, the scanner motor makes two short attempts to move. The gear does not turn freely, so the printer stops and displays Error 100016. How can I determine whether the gears are jammed or the motor is defective? It is especially frustrating because the scanner failure prevents me from using the printer, even though I do not need the scanning function.

Answer

What Epson Error 100016 Means

Error 100016, sometimes displayed together with E-02, generally indicates that the printer could not complete the scanner's startup or home-position sequence. When the printer powers on, the scanner control system expects the Contact Image Sensor, or CIS carriage, to move in a particular direction and reach its home position within a limited time.

If the expected movement or home-position signal is not detected, the control board stops the motor and reports Error 100016. Possible causes include:

• Incorrectly positioned or binding scanner gears

• A foreign object obstructing the scanner carriage

• A displaced, loose, or damaged scanner drive belt

• Cracked, stripped, or contaminated gear teeth

• A scanner carriage that cannot move smoothly along its guide

• A home-position sensor or sensor flag problem

• A loose, damaged, or incorrectly seated scanner ribbon cable

• A stalled or electrically defective scanner motor

• A defective CIS unit or scanner-control circuit

• In less common cases, a mainboard failure

The two short bursts you hear are likely the printer commanding the scanner motor to move and then checking for the expected feedback. When it does not detect the correct movement or home position, it stops the startup process to prevent further mechanical or electrical damage.

Should the Scanner Gears Turn Freely by Hand?

Not necessarily. A scanner gear train may feel stiff or may not rotate freely while fully assembled. The angle of the gear teeth, reduction ratio, belt tension, and internal resistance of the motor can make the mechanism difficult-or sometimes impractical-to back-drive by hand. Therefore, resistance alone does not prove that the motor has failed or that the gears are jammed.

You should not force a gear that does not rotate easily. Applying excessive pressure can strip the plastic teeth, crack a gear hub, stretch the belt, or damage the motor. A small amount of controlled movement may be possible on some models, but the mechanism should not be judged solely by whether the exposed gear spins freely.

Another viewer with a similar problem removed both gears and carefully checked the motor shaft with a small screwdriver. After confirming that the shaft was not physically seized, the viewer reinstalled and reseated the gears, reconnected the scanner, and found that it worked normally. This experience suggests that gear seating, alignment, or the mechanism's assembly position can sometimes cause Error 100016 even when the motor itself is functional.

However, being able to rotate the motor shaft manually only shows that it is not mechanically locked. It does not confirm that the motor's windings, driver circuit, or electrical connection is working correctly.

Inspecting the Scanner Mechanism

Disconnect the printer's power cord before opening or touching the scanner assembly. Do not rely only on the power button, since the printer may still contain energized circuits while connected to an outlet.

First, examine the complete gear train under good lighting. Look for damaged teeth, hair, paper fibers, dried lubricant, loose hardware, or a gear installed above or below its correct position. A gear can appear normal while sitting slightly crooked on its shaft, which may cause it to bind under motor load.

Remove and reinstall only the gears necessary for inspection. Take photographs before disassembly so that you can reproduce their original positions. Check that each gear is fully seated, meshes evenly with the adjacent gear, and does not rub against the housing or cover.

If the gear train uses timing marks or must be installed in a particular starting position, preserve that relationship. A mechanism may rotate normally but still fail initialization if a cam, lever, or sensor flag is positioned incorrectly.

Check the Scanner Carriage and Belt

With the printer unplugged, inspect the scanner carriage beneath the glass. Depending on the model and scanner design, the carriage may offer some resistance because it remains connected to the belt and motor. It should not be wedged against the frame or blocked by debris.

Inspect the scanner belt for the following conditions:

• Missing or worn teeth

• Excessive looseness

• Twisting

• Separation from the motor pulley

• Incorrect routing

• Oil or lubricant on the belt

• A belt clamp that has detached from the scanner carriage

Also examine the guide rail and the carriage's sliding surfaces. Old grease, dirt, or a distorted housing can create enough resistance to stall the small scanner motor. If cleaning is necessary, avoid placing lubricant on the belt, pulleys, glass, optical components, or encoder surfaces. Do not use excessive lubricant because it can spread into the optical system and contaminate the scanner.

Check the Home-Position Detection System

Error 100016 can occur even when the motor and gears move because the printer still must recognize that the scanner carriage reached its home position. Inspect the home-position sensor, actuator tab, and any related encoder components.

A sensor flag can become bent, displaced, or trapped on the wrong side of the sensor during reassembly. Dust or ink mist may also interfere with optical sensing. Make sure the flag enters the sensor correctly and that no cable is blocking its movement.

If your scanner uses an encoder strip or encoder wheel, inspect it for contamination, damage, or incorrect installation. Handle encoder components carefully and avoid scratching or stretching them. A scanner that physically moves but cannot measure its position may still produce the same error.

Inspect the Cables and Connections

A loose scanner ribbon cable can prevent the printer from detecting movement, reading the CIS unit, or operating the motor correctly. With the printer unplugged, inspect the scanner's flexible flat cables and wire connectors.

Check for:

• A cable inserted crookedly

• A connector that is not fully locked

• Torn or creased ribbon conductors

• Corrosion or ink contamination

• Exposed or burned contacts

• A cable installed backward after repair

• Damage near hinges or other flexing points

Do not repeatedly insert and remove ribbon cables with the printer connected to power. A misaligned cable can short adjacent contacts and damage the scanner circuit or mainboard.

Distinguishing a Mechanical Jam From a Motor Problem

If the gears and belt are removed and the carriage moves smoothly along its track, the binding is more likely located in the gear train, belt routing, pulley, or motor. If the carriage remains difficult to move after it is disconnected from the drive system, inspect the rail, carriage guides, housing, and nearby obstructions.

If the motor shaft is completely seized when isolated from the gears, the motor may be mechanically defective. If the shaft moves normally but the motor only pulses or does not rotate during startup, possible causes include a weak motor, damaged wiring, a poor connector, or a motor-driver problem on the circuit board.

Electrical motor testing requires the correct service information and test equipment. Applying external voltage directly to an unidentified scanner motor is risky because the required voltage, polarity, and drive method can vary. An incorrect test can damage the motor or scanner electronics.

Why the Printer Stops Even When the Scanner Is Not Needed

On many Epson multifunction printers, the scanner is part of the startup self-test. The printer firmware will not enter its normal ready state until every required subsystem completes initialization. Consequently, a failed scanner can prevent printing, copying, and other functions even when the user only wants to print.

There normally is no supported menu option to disable the scanner or bypass Error 100016. The printer must detect normal scanner initialization before it will finish starting. Attempting to trick or bypass the sensor may cause the carriage to strike the frame or allow the motor to continue driving a jammed mechanism.

After reseating the gears, cables, and scanner components, reassemble enough of the mechanism that it can operate safely before testing it. Keep hands, tools, and loose cables away from moving components during startup. If the scanner again makes two attempts and stops, disconnect the power rather than repeatedly cycling it, since repeated stalls can place unnecessary stress on the motor and its driver circuit.

Addressing printer issues can be difficult because many diagnoses require direct inspection and hands-on testing. For that reason, we cannot provide individualized remote troubleshooting or repair support. We do offer in-person evaluation and repair through our local printer diagnostic facility [https://bchtechnologies.com/printer-repair-service]. Due to high demand, service is handled on a first-come, first-served basis, and it may take several weeks before a printer can be scheduled for drop-off. We can repair either a complete printer or certain individual components, with instructions provided for each service. We also recognize that professional repair is not always the most economical option, so we strongly encourage self-guided research. A good starting point is YouTube or the homepage of our BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies]. Use the search icon near "About" on the right side of the channel menu to search for your printer model, error code, or component. We receive dozens of questions each day about specific videos, and after nine years of publishing repair content, it is difficult to remember every video individually. YouTube's search feature is usually the fastest way to locate the appropriate material and may also recommend useful videos from other repair channels.

Thank you again for watching our video and for sharing such a detailed description of the symptoms. We appreciate your support and hope these checks help you determine whether the problem is caused by gear alignment, carriage resistance, position detection, wiring, or the scanner motor itself.