Epson ET-8550 Carriage Crash, Error 000031, and Transportation Lock Fault - How to Diagnose and Fix

Customer Question

I've been having major issues with my Epson ET-8550. It started with error 000031, where the printhead carriage slams into the left side. I've fixed this before using a video, but this time I couldn't catch it and tried taping over the sensor hole. After that, the printer began acting confused-like it couldn't tell where it was. Eventually, the capping station clogged, and while trying to fix it, I accidentally broke it.

I installed a replacement capping station, but it stayed stuck in the up position. When the printer tried to home itself, the printhead kept hitting the cap, so I manually held it down with a screwdriver. Then I got a transportation lock error, and when I rebooted, the printer immediately showed the same lock fault again. Now the carriage is stuck as if it's locked, and I can manually unlock it, but it continues to be a problem.

Is there anything I can do to get this machine "back in time"? I've tried everything I can think of. Any help would be appreciated.

Answer

We at BCH Technologies deeply appreciate your support and engagement, particularly through our YouTube channel (BCH Technologies on YouTube - https://youtube.com/@bchtechnologies). Your feedback is extremely valuable and helps us continue improving our technical expertise and video library.

Understanding the Errors and Mechanical Problems

1. Error 000031 - Carriage Crash on the Left Side

Error 000031 on Epson printers is related to the CR home position failure. In everyday terms, the printer cannot detect the left-side optical sensor, so the carriage keeps driving until it physically hits the rail or wall.

Normally, the cause is one of the following:

• The CR home sensor is blocked.

• The APG (Auto Paper Gap) lever is misaligned or triggered incorrectly.

• A CIS (Continuous Ink System) tube or aftermarket part interferes with the sensor hole.

• Timing of the carriage movement gets disrupted when the mechanism can't initialize properly.

You mentioned taping over the hole that the printer uses to detect home position. Unfortunately, that blocks the CR sensor's ability to detect the home flag, leading to exactly the "confused movement" you described. The printer essentially has no idea where the carriage is anymore.

2. Capping Station Failure and Replacement

When the capping station broke and you replaced it, another issue was introduced: the new capping station was stuck in the UP position.

This creates a secondary failure:

• The printhead cannot cross the capping station.

• The firmware detects resistance and flags a transport-related error.

• Holding it down manually can let the carriage pass, but the printer still thinks something is obstructing the home sequence.

3. Transportation Lock Error Appearing Immediately on Startup

This usually occurs when:

• The carriage lock lever (sometimes called the transportation lock) is engaged.

• The APG lever is stuck in the wrong position.

• The CR belt tension changes because the carriage wasn't allowed to initialize properly.

• The printer detects that the carriage cannot move freely during startup.

In the ET-8550, there is no "timing" in the traditional gear-based sense. Instead, it uses a combination of:

• Optical encoder strip

• CR home sensor

• APG position lever

• Firmware-controlled initialization sequence

When one of these is out of sync, the printer behaves like it's "out of time," even though there is technically no mechanical timing gear to reset.

4. Most Likely Root Cause in Your Case

Your description strongly suggests that your CIS tubing or installation interfered with the APG lever on the carriage. When this lever gets bent, stuck, or mis-triggered, the printer:

• Misreads paper gap

• Fails its carriage home test

• Slams into the wall

• Throws error 000031

• And later, triggers the transportation lock fault

Once the APG lever is compromised, the printer cannot calibrate its home position, cannot judge height clearance, and cannot move correctly during startup.

This is why you're seeing multiple symptoms across different parts of the machine.

5. The Fix Going Forward

Based on everything you described, the issue lies in the APG lever mechanism on the carriage (CR unit).

I will be making a video on how to bypass the APG lever so the printer can initialize properly again. Please follow our channel and the video should be available in a few days:
BCH Technologies on YouTube (https://youtube.com/@bchtechnologies)

This workaround will allow the printer to home correctly and eliminate both the 000031 error and the transportation lock fault.

Important Note About Troubleshooting

Handling printer issues can be extremely hands-on, and unfortunately, we can't offer remote troubleshooting or repair guidance beyond general direction. We do provide in-person diagnostic and repair services through our local facility (Printer Repair Service - https://bchtechnologies.com/printer-repair-service). Because of high demand, service is first-come, first-served, and wait times can be a few weeks.

Our services allow you to repair the whole printer or individual parts, but we understand that our rates may not be the lowest. For those who prefer self-help, we strongly encourage searching online or visiting our YouTube channel's homepage (BCH Technologies YouTube - https://youtube.com/@bchtechnologies). Use the search icon next to "About" to find videos quickly; with nine years of videos, even I can't remember every topic, but YouTube search can. It may also suggest helpful videos from other creators.

Thank you again for supporting us, for your patience, and for being a continued part of the BCH Technologies community. Your trust means a great deal to us, and we'll keep working hard to provide resources that help you keep your equipment running.