Epson ET-8550 Error Codes 000043 and 000031: Paper Feed, Encoder, and Carriage Troubleshooting

Question

My Epson EcoTank ET-8550 is currently showing error code 000043. Based on videos I watched on the BCH Technologies YouTube channel, I thought this might be related to the PW (paper width) sensor, so I ordered a replacement sensor. Before the printer started displaying 000043, however, it was showing error code 000031.

Is replacing the PW sensor the right next step, or should I order any other parts at the same time? I live in Mississippi and have been unable to find anyone locally who repairs this printer.

Answer

Error 000043 Is Not Specifically a PW Sensor Error

There is one important correction I would make before you purchase any additional parts.

On the Epson ET-8550, error code 000043 is not specifically defined as a PW sensor failure. According to the ET-8500/ET-8550 service information, 000043 is a PF PID reverse error, meaning that the printer detected an abnormal condition in the PF (paper-feed) drive system. The documented causes include excessive mechanical resistance or an obstruction in the paper-feed mechanism, damaged or disengaged gears, contamination of the PF encoder scale, a damaged or improperly connected PF encoder FFC, failure of the PF encoder, or-in less common cases-a mainboard problem.

Therefore, although replacing the PW sensor may be worthwhile if you have independent evidence that the PW sensor is damaged, contaminated, or malfunctioning, I would not assume that a new PW sensor will automatically clear error 000043.

Since you have already ordered the PW sensor, you can certainly inspect and replace it if appropriate, but I would not order a collection of additional parts until you have examined the PF system and seen what happens after the work you already planned.

What to Check for Error Code 000043

For 000043, I would concentrate first on the paper-feed mechanism rather than purchasing another electronic component.

With the printer powered off and unplugged, inspect the entire accessible paper path for a small piece of paper, label material, foreign object, dried ink buildup, or another obstruction. Something very small can sometimes interfere with a mechanism even though there is no obvious sheet of paper jammed inside.

You should also inspect the gears and moving portions of the paper-feed mechanism. A gear that has slipped out of engagement, cracked, or lost teeth can cause the PF motor to move the mechanism differently from what the printer expects.

Another important component is the PF encoder system. The ET-8550 monitors movement of the paper-feed mechanism through an encoder. If the encoder scale is contaminated or the encoder sensor cannot read it properly, the mainboard can interpret the movement incorrectly and generate a PF positioning error. Epson's service information for 000043 specifically directs attention to the PF scale, PF encoder FFC/connector, PF encoder, and mainboard after mechanical obstructions have been ruled out.

Be especially careful around encoder components. They should not be scratched, bent, coated with grease, or aggressively cleaned.

Why the Earlier Error Code 000031 Matters

The fact that the printer previously showed error code 000031 is also an important clue, but it represents a somewhat different system.

For the ET-8550, 000031 is a CR load position excess load error. "CR" refers to the carriage-the assembly carrying the printhead back and forth across the printer.

The service information lists possible causes such as:

• An obstruction in the carriage travel area

• Excessive mechanical resistance

• Interference involving the ink system

• A disengaged or damaged gear

• A loose, frayed, or jumping carriage timing belt

• Contamination affecting the carriage encoder scale

• A carriage motor that is beginning to fail

• A mainboard problem

The recommended diagnostic sequence includes inspecting the carriage travel area, CR lock and ink system, timing belt, carriage movement/load, CR drive mechanism, and CR encoder scale before moving toward motor or mainboard replacement.

That means 000031 is also not simply a PW sensor code.

Check the Carriage and APG Area Carefully

Because your printer showed 000031 before changing to 000043, I would pay close attention to anything mechanically connecting the carriage system and paper-feed system.

On an ET-8550, the printer performs several mechanical operations during startup. The carriage, paper-feed drive, ink system, carriage lock, and related mechanisms have to reach their expected positions in the correct sequence.

Inspect the carriage travel path for anything that could cause resistance. With the printer safely powered off and only where the mechanism permits movement without forcing it, check for unusual binding, displaced cables, foreign objects, damaged tubing, or anything else interfering with carriage travel.

The CR encoder strip/scale and timing belt also deserve inspection. A contaminated encoder scale can prevent the printer from accurately determining carriage position. A loose or damaged timing belt can similarly cause the actual carriage movement to differ from what the electronics expect.

The APG (automatic platen gap) mechanism is also worth visually inspecting because it interacts mechanically with the printer's positioning system. If a lever, gear, or associated mechanism is stuck or out of position, initialization may fail. However, I would avoid replacing the APG assembly-or any other assembly-simply because error 000031 appeared. The code can be generated by several different mechanical conditions.

What About the PW Sensor You Already Ordered?

Since the sensor has already been ordered, there is no harm in carefully inspecting the existing PW sensor and comparing it with the replacement.

Check the sensor itself, its FFC/cable, and the connector. Make sure the cable is not torn, creased, partially inserted, or inserted at an angle. Also make sure the sensor is seated in the correct position.

If the printer has previously been disassembled, cleaned, modified, or converted for another printing application, carefully look for anything that may have been moved during that work.

However, I would treat the PW sensor replacement as one diagnostic step rather than a confirmed repair for error 000043.

I Would Not Order More Parts Yet

At this point, I would not recommend ordering additional parts just because you have seen both 000031 and 000043.

Replacing parts one after another can become expensive very quickly, and these codes do not uniquely identify one failed component.

Instead, after installing or inspecting the PW sensor, pay close attention to the printer's startup behavior. In particular, observe:

• Whether the carriage begins moving normally

• Whether it stops or hesitates at a particular location

• Whether the paper-feed mechanism turns

• Whether you hear clicking, grinding, buzzing, or repeated attempts to move

• Whether the error occurs immediately or only after several seconds of initialization

• Whether the code remains 000043, returns to 000031, or changes to another code

The sequence immediately before the error is often just as valuable diagnostically as the number displayed on the screen.

The transition from 000031 (carriage-load/position problem) to 000043 (paper-feed reverse-position problem) may indicate that the machine has a broader mechanical initialization problem rather than two unrelated failed sensors. That does not automatically mean the mainboard is bad. Mechanical resistance, encoder-reading problems, damaged gears, or a mechanism that is out of synchronization should generally be investigated before replacing an expensive board. Epson also provides the ET-8550 user documentation and support resources for normal operating and error-message guidance.

Addressing printer problems can be complicated because so much of the diagnosis depends on physically observing and testing the machine. For that reason, we're not able to provide ongoing remote troubleshooting, repair suggestions, or step-by-step support for individual printer repairs. We do offer an in-person evaluation and repair service through our local printer diagnostic and repair facility [https://bchtechnologies.com/printer-repair-service]. Because demand is high, repairs are handled on a first-come, first-served basis, and it may take several weeks before we can accept a printer for drop-off. Our services can cover either a complete printer or certain individual components, and the service page explains how to proceed. We also recognize that professional repair may not be the most economical solution for every situation, so we strongly encourage self-help research when practical. A good place to begin is YouTube or the homepage of our BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies]. On our channel, use the search icon near the "About" section on the right side of the menu and search terms such as ET-8550 000043, ET-8550 000031, ET-8550 PF encoder, ET-8550 paper feed, ET-8550 carriage, or ET-8550 APG. We receive dozens of questions every day asking whether we have a video covering a particular repair. After producing videos for more than nine years, it is difficult to remember every individual video, so searching directly within the channel is usually the fastest approach. YouTube may also recommend useful videos from other repair channels covering the same problem.

Thank you again for contacting BCH Technologies and for supporting our YouTube channel. We sincerely appreciate your encouragement, and I hope this clarification keeps you from purchasing unnecessary parts while you work through the 000043 and 000031 errors on your ET-8550.