Epson ET-8550 Extended Output Tray Error After Fixing Error Code 031002: Stacker Sensor Troubleshooting Guide

Question

I installed a replacement printhead in my Epson EcoTank ET-8550 after waiting about a month for the part. The new printhead successfully cleared error code 031002, which is great, but the printer still has a problem involving the extended output tray.

Is there a sensor for the extended tray that can be tested or bypassed? How should I diagnose and repair this remaining issue?

Answer

First, it is excellent news that replacing the printhead resolved Epson error code 031002. That code is generally associated with an electrical or thermal detection problem involving the printhead, its circuitry, or the connection between the printhead and the mainboard. Since the error disappeared after the printhead was replaced, your original diagnosis was likely correct.

The extended tray problem is probably a separate issue involving the ET-8550's output tray, which Epson may also refer to as the stacker. The printer uses a leaf-style position sensor to determine whether the output tray mechanism is in the expected position. If the sensor does not change state when the tray opens, closes, extends, or retracts, the printer may continue reporting a tray-related condition even though the major printhead error has been resolved.

Locating the ET-8550 Stacker Sensor

The ET-8550 stacker sensor is connected to the printer's mainboard at connector CN14. From CN14, the sensor wiring travels toward the front of the printer and mounts near the front paper guide assembly.

To identify the exact components, search for SKU REF-ET8550-Parts on the BCH Technologies website [https://bchtechnologies.com]. This is the ET-8550 Exploded Parts Diagram - Repair Reference Guide, Annotated Edition.

The guide provides a professionally organized, exploded-diagram view of the Epson ET-8550's internal assemblies. It can help you:

• Identify individual components and their locations.

• Understand how the printer's assemblies fit together.

• Follow the disassembly sequence more accurately.

• Locate replacement parts associated with the output tray.

• Open linked product pages for parts that are available.

• Find related repair videos through the YouTube icons shown beside supported components.

The guide is updated as new parts, repair information, and videos become available. Customers with access to the guide can receive the latest version when it is updated.

After opening the reference guide, press Ctrl+F on Windows or Command+F on a Mac to open the document search field. Search for front paper guide. This should direct you to page 3, where the front paper guide appears near the upper-right area of the diagram.

The two parts most relevant to your tray problem are:

• Part 537 - Leaf Sensor

• Part 530 - Wire for the Leaf Sensor

These components make up the sensing circuit that reports the tray or stacker position to the mainboard.

What to Inspect

Before attempting to bypass anything, inspect the sensor and its mechanical actuator carefully. Permanently bypassing the sensor is generally not recommended because the printer expects the sensor signal to change as the tray moves. A fixed bypass may clear one condition but create another, interfere with tray movement, or allow the printer to operate while the mechanism is in an unsafe position.

Start by examining the leaf sensor itself. A small plastic lever, flag, or tab should physically move the sensor when the output tray changes position. If this actuator is broken, bent, displaced, or no longer reaching the sensor, the electronic sensor may be functional but unable to detect the tray.

Gently operate the sensor lever by hand and confirm that it moves freely. It should not remain stuck in one position. Dust, dried ink, paper debris, a displaced spring, or a damaged plastic tab may prevent it from returning correctly.

Next, inspect the wire identified as part 530. Follow the wiring from the leaf sensor toward the mainboard and check for:

• A loose connector.

• A partially seated plug.

• Pinched or crushed wires.

• Damage caused during printhead replacement.

• Corrosion or contamination at the connector.

• A wire pulled tight by an incorrectly routed cable.

• A broken conductor hidden inside intact-looking insulation.

Pay particular attention to connector CN14 on the mainboard. Turn the printer off and disconnect it from power before touching the connector. Confirm that the plug is inserted evenly and completely. Do not force the connector, because the socket or solder joints can be damaged.

Since you recently replaced the printhead, it is possible that the tray sensor wiring was moved, pinched, or partially disconnected during disassembly and reassembly. The sensor cable may also have been routed on the wrong side of a frame or plastic guide, preventing the tray mechanism from moving normally.

Testing the Leaf Sensor

If you have a multimeter and are comfortable testing small electronic components, you may be able to check whether the leaf sensor changes state when its lever is pressed and released.

Depending on the exact sensor design, it may behave as a mechanical switch or an optical-type sensor. A mechanical leaf switch should show continuity in one position and an open circuit in the other. An optical sensor may require powered voltage testing and should not be treated like a basic continuity switch without first identifying its pin configuration.

Do not apply outside voltage to the sensor or CN14. Applying voltage to the wrong pin can damage the mainboard.

A safe first test is to disconnect the printer from power, unplug the sensor connector, and inspect the relevant contacts for an obvious change in continuity as the actuator moves. If no change occurs, the sensor may be defective. If the sensor changes normally, the problem is more likely to involve the wiring, connector, mechanical tray actuator, or mainboard input circuit.

You can also temporarily operate the sensor lever by hand while observing whether the printer's tray warning changes. This can help confirm whether the printer recognizes the sensor transition. Keep your hands, tools, and loose clothing away from moving gears and tray components whenever the printer is powered.

Why a Permanent Sensor Bypass May Not Work

The printer may check for more than a simple open or closed signal. It may expect the stacker sensor to change state during startup or while the tray motor operates. If the sensor is permanently held in one condition, the printer may interpret that as:

• The tray being stuck open.

• The tray being stuck closed.

• The tray failing to move.

• A motor or gear malfunction.

• An obstruction in the tray mechanism.

• A sensor that never changes state.

For this reason, manually moving the sensor is useful as a diagnostic test, but permanently bridging, cutting, or bypassing the sensor wires is usually not a reliable repair.

Inspecting the Output Tray Mechanism

If the sensor and wiring appear functional, examine the mechanical tray system. The output tray may not be traveling far enough to activate the sensor.

Look for:

• Broken or missing gear teeth.

• A tray that is installed slightly out of alignment.

• A disconnected spring.

• A damaged tray rack or drive gear.

• A foreign object blocking movement.

• A cracked plastic actuator near the leaf sensor.

• A motor that runs without moving the tray.

• A tray mechanism that stops before reaching its final position.

Slowly move the tray by hand only where the mechanism permits it. Do not force it against motor resistance. Watch the leaf sensor actuator while moving the tray and determine whether the actuator actually presses and releases the sensor at the proper points.

If operating part 537 manually changes the printer's response, but moving the tray does not, the sensor is probably working and the mechanical actuator is not reaching it. If manually operating the sensor makes no difference, focus on part 530, connector CN14, the sensor itself, or the mainboard sensing circuit.

Working with parts 537 and 530 should help you narrow the problem down to one of four areas: the sensor, its wiring, the mechanical actuator, or the mainboard connection. The exploded reference guide will make it much easier to identify the pieces without guessing.

Addressing printer issues can be complicated because many faults require direct observation, disassembly, electrical testing, and hands-on inspection. For this reason, we are unable to provide individualized remote troubleshooting, repair instructions, or ongoing technical support for 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, printers are handled on a first-come, first-served basis, and it may take several weeks before an appointment or drop-off opening becomes available. Our services can cover either an entire printer or certain removable parts, and the service page provides instructions for proceeding with each option.

We also recognize that professional repair rates may not be the most economical choice for every customer. Therefore, we strongly encourage using online research and self-help resources when appropriate. You can begin with YouTube or visit the homepage of our BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies].

To locate a particular repair video, use the search icon near the About section on the right side of the channel menu. We receive dozens of questions each day asking whether we have a video on a specific repair. Since we have produced repair content for more than nine years, it is difficult to remember every video by title. Using the channel's search function is usually the fastest way to find the most relevant material. YouTube may also recommend helpful videos from other creators covering the same sensor or tray mechanism.

Thank you again for sharing your update and for confirming that the replacement printhead resolved error code 031002. Your detailed observations are genuinely helpful, and we appreciate your patience and continued support of BCH Technologies.