Epson Error 100077 After Replacing Scanner Motor, FFC Cables, and Scanner Bar: What to Check Next

Question

I followed the previous troubleshooting steps for my Epson printer and even replaced the scanner motor, the FFC cables, and the scanner bar with new parts. After installing everything and reassembling the printer, I still have exactly the same problem and the same error. What should I check next, and how can I determine which part of the scanner system is actually causing the failure?

Answer

The important thing at this point is not to replace more parts all at once. Instead, break the 100077 error down piece by piece and determine exactly where the scanner movement sequence stops.

What Does Epson Error 100077 Mean?

The 100077 error is generally associated with a failure involving the scanner movement system. In practical terms, the printer is attempting to initialize or move the scanner mechanism but is not detecting the movement it expects.

That does not necessarily mean the scanner motor itself is defective. The scanner system is a chain of components, and a failure anywhere along that chain can produce essentially the same symptom.

The system may involve:

• The scanner motor

• The scanner motor cable or FFC connection

• The scanner carriage or scanner bar

• The scanner drive belt and gears

• The scanner carriage position or home-position detection system

• The scanner FFC cables

• Connectors on the scanner assembly

• Connectors on the mainboard

• The mainboard's scanner motor driver circuit

• Mechanical resistance preventing the scanner from traveling

Since you have already replaced the scanner motor, FFC cables, and scanner bar, the next step is to determine whether the printer is actually commanding the scanner motor to move.

Step 1: Test the Scanner Motor Before Fully Reassembling the Printer

You do not necessarily have to close and completely reinstall the scanner cover every time you test it.

With the printer powered off, connect the scanner motor and its appropriate cable or FFC connection correctly. Make sure the cable is inserted completely straight and is seated to the proper depth.

Then position the scanner assembly so you can safely observe the mechanism during startup.

Power the printer on and watch the scanner motor.

The first question is very simple:

Does the scanner motor attempt to move?

This single test divides the troubleshooting process into two completely different directions.

Be careful whenever operating a partially disassembled printer. Keep your hands, tools, loose clothing, and conductive objects away from moving mechanisms and exposed electronic areas. Always turn the printer off and disconnect power before plugging, unplugging, or repositioning FFC cables.

If the Scanner Motor Does Not Move

If the scanner motor does absolutely nothing during initialization, replacing the scanner motor itself may not solve the problem because the motor may never be receiving the command or electrical power required to operate.

Start by checking the scanner motor connection again.

FFC cables can be deceptive. A cable may appear connected while actually being slightly crooked, inserted too shallowly, inserted on the wrong side of a connector, or installed with the contact surface facing the wrong direction.

Inspect both ends carefully.

Look for:

• FFC cable inserted crooked

• Cable not inserted completely

• Cable contacts facing the wrong direction

• Broken or folded conductive traces

• Damaged connector locking tabs

• Bent connector contacts

• Contamination such as ink or cleaning liquid

• Torn cable ends

• Incorrect cable routing

• Cable pinched during reassembly

A brand-new FFC cable does not eliminate a connection problem. If the connector itself is damaged, replacing the cable will not correct it.

Check the Mainboard Connector

If the motor and cable are known to be good but the motor never receives a movement command, the next point in the chain is the electronics controlling the scanner.

Carefully inspect the corresponding mainboard connector.

A damaged connector can have:

• Bent internal pins

• Broken solder joints

• Cracked plastic

• Missing locking tabs

• Corrosion

• Liquid contamination

• A partially lifted connector

If the printer was previously disassembled, it is also possible for an FFC cable to have been inserted incorrectly and damaged the connector.

If the scanner motor receives no drive signal even though the motor and wiring are correct, the problem can eventually lead back to the scanner motor driver circuitry on the mainboard.

That is one reason replacing the scanner motor alone does not always resolve error 100077.

If the Scanner Motor Moves, Go to the Next Part of the System

If you turn the printer on and see that the scanner motor actually turns, that is extremely useful information.

It tells you that the printer is at least attempting to operate the scanner motor.

Now stop focusing on the motor itself and move to the next component in the mechanical chain.

Ask:

Does the motor's rotation actually move the scanner carriage?

If the motor rotates but the scanner carriage stays stationary, inspect the drive mechanism.

Depending on the model, this can include the scanner drive belt, pulley, gears, shaft, or other mechanical transfer components.

Look for a belt that is:

• Loose

• Disconnected

• Installed incorrectly

• Slipping on a pulley

• Damaged

• Missing teeth

Also inspect gears for cracks, missing teeth, or gears that turn freely on their shafts instead of transferring power.

Check Whether the Scanner Carriage Moves Freely

With the printer powered off and unplugged, inspect the scanner carriage mechanically.

The scanner carriage should be able to travel along its intended path without excessive resistance.

Do not force it.

You are looking for anything that prevents normal movement, including:

• Scanner bar installed incorrectly

• Carriage installed incorrectly on the guide

• Drive belt routed incorrectly

• FFC cable folded into the scanner's travel path

• Cable catching underneath the carriage

• Foreign object inside the scanner

• Scanner glass frame pressing against the carriage

• Mechanical component installed backward

• Excessive friction on the scanner rail

• Carriage contacting the housing

This is especially important after replacing the scanner bar because the problem may not be the new component itself. A cable, guide, bracket, spring, or other part may have shifted during reassembly and now physically blocks movement.

Watch What Happens During Startup

Instead of simply seeing the 100077 error and stopping there, watch the entire scanner initialization sequence.

For example, determine whether the scanner:

1. Does not move at all.

2. Moves slightly and stops.

3. Moves in one direction but cannot return.

4. Moves until it physically hits one side.

5. Makes a clicking or grinding sound.

6. Moves normally but still generates error 100077.

7. Repeatedly attempts to find its home position.

Each behavior points toward a different type of failure.

If there is absolutely no movement, think primarily about the motor electrical circuit.

If the motor runs but the carriage does not move, think about the belt or mechanical drive system.

If the scanner carriage moves but crashes into the end of its travel or repeatedly searches for position, think about scanner position detection or home-position sensing.

If the scanner moves normally but 100077 still appears, then the printer may not be receiving the expected feedback signal even though the mechanical movement looks normal.

Check the Scanner Home Position

During startup, the printer needs to establish where the scanner carriage is located.

If the scanner physically moves but cannot establish its starting or home position, the printer may continue trying to move the carriage until it eventually reports an error.

Therefore, inspect the scanner's home-position area carefully.

Look for:

• Sensor blocked by debris

• Sensor flag incorrectly positioned

• Plastic actuator installed incorrectly

• Cable disconnected from the sensor

• FFC cable damaged or incorrectly seated

• Scanner carriage unable to reach the home position

• Mechanical interference near the end of travel

A position-detection problem can look remarkably similar to a motor problem because the printer only knows that the scanner failed to complete the movement it expected.

New Parts Do Not Automatically Rule Out Those Circuits

Since you replaced the scanner motor, scanner bar, and FFC cables, it is understandable to assume those parts can now be eliminated completely.

However, the important distinction is between replacing a component and verifying the entire circuit.

For example, a new scanner motor connected to a damaged mainboard connector will behave exactly like the old motor.

A new FFC cable inserted into a connector with a bent contact can produce exactly the same error.

A new scanner bar attached to a binding carriage can produce exactly the same failure.

That is why I recommend stopping the parts-replacement process temporarily and diagnosing one function at a time.

A Useful Diagnostic Sequence for Error 100077

For Epson error 100077, I would approach the problem in this order:

First, verify whether the scanner motor receives a command and physically moves.

If the motor does not move, inspect the motor connection, cable, FFC connections, connectors, and eventually the mainboard motor-control circuit.

If the motor moves, verify whether that movement is transferred through the belt or gears to the scanner carriage.

If the carriage moves, verify that it moves smoothly throughout its normal travel range.

If the carriage travels correctly, determine whether the printer recognizes the scanner's home or position signal.

This method prevents you from replacing several more parts without knowing whether they are related to the failure.

The key question right now is therefore not simply whether the replacement scanner motor is new. The important question is:

When the printer powers on, does that scanner motor actually attempt to turn?

That observation will tell you which direction to investigate next.

Addressing printer problems can be complicated because many failures require hands-on inspection, testing, and observation of the machine while it operates. For that reason, we're unable to provide ongoing remote troubleshooting, repair diagnosis, or individualized repair support. We do offer an in-person evaluation and repair service through our printer diagnostic and repair facility [https://bchtechnologies.com/printer-repair-service]. Because of the volume of printers we receive, service is handled on a first-come, first-served basis, and it may take several weeks before an appointment or drop-off can be accommodated. Our services can address either an entire printer or certain individual components, depending on the situation, and the service page explains how to proceed. We also understand that professional repair may not be the most economical option for every printer. For that reason, we strongly encourage self-help research whenever practical. You can begin with YouTube or visit the BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies]. On our channel homepage, use the search icon near the "About" section to search for your printer model, 100077 error, scanner motor, scanner assembly, FFC cable, or another specific symptom. I receive dozens of questions every day asking whether we have a video on a particular subject, and after creating repair videos for more than nine years, it is difficult to remember every video individually. YouTube's channel search is usually the fastest way to locate relevant material, and YouTube may also recommend useful repair videos from other creators.

Thank you again for your continued support, for purchasing the replacement components from us, and especially for taking the time to explain what you have already tested. I hope breaking error 100077 into individual electrical and mechanical stages helps you narrow the problem instead of continuing to replace parts without knowing which section of the scanner system is actually failing. We sincerely appreciate your engagement with BCH Technologies and wish you the best with the repair.