Epson ET-8550 Phantom Paper Jam on Startup: PE Sensor vs Mainboard and What to Check First

Question

My Epson ET-8550 keeps showing a paper jam even though there's no paper actually feeding. The error happens immediately on startup, before any sheet moves, and the printer even pushes the paper tray out by itself without a print job. Could this be caused by a bad PE (paper eject) sensor, and is that something I can replace at home?

Answer

Based on the symptoms you described, there are two primary possibilities to consider:

1. a faulty or falsely triggered PE (Paper Eject) sensor, or

2. an issue on the mainboard that is misinterpreting sensor signals.

Let's break this down in a practical way.

Why this looks like a "phantom" paper jam

When an ET-8550 reports a paper jam immediately at startup, without pulling a sheet, it means the printer believes paper is already present somewhere along the paper path. Because the printer thinks paper is "stuck," it may:

• Trigger a paper jam error as soon as it powers on

• Eject or partially open the paper tray automatically

• Refuse to initialize for printing, even with no job sent

This behavior almost always points to a sensor state problem, not a mechanical jam.

Possibility 1: Failed or stuck PE (Paper Eject) sensor

The PE sensor monitors whether paper has exited the paper path correctly. If this sensor is:

• Electrically failed

• Contaminated with dust, paper debris, or ink mist

• Mechanically stuck in the "paper present" position

...the printer will think paper is jammed even when the path is empty.

In that case, replacing the PE sensor can absolutely resolve the issue. The correct part for the ET-8550 is shown here:
ET-8550 PE (Paper Eject) Sensor (https://bch-youtube-fan-store.myshopify.com/products/epson-paper-eject-pe-sensor-cd28-sns-sensor-for-et8550)

Can this be replaced at home?

Yes-if you are comfortable with partial disassembly and careful handling of ribbon cables and small connectors. However, it's not a simple "pop-out, pop-in" job. Replacing the PE sensor typically involves:

• Opening the printer casing

• Accessing the paper path area

• Disconnecting and reconnecting sensor wiring correctly

If a connector is misaligned or damaged during installation, you can introduce new faults.

Possibility 2: Mainboard misreading sensor input

If the PE sensor itself is good, the next likely cause is the mainboard. The board processes input from all paper path sensors. If a circuit on the board fails or becomes unstable, it can falsely interpret a normal sensor signal as a jam condition.

Signs that point more toward a mainboard issue include:

• The problem persists even after disconnecting or replacing the PE sensor

• Multiple paper-related behaviors happen at once (phantom jam, tray ejecting, startup interruption)

• The issue appeared suddenly without gradual feeding problems

In these cases, replacing the PE sensor alone would not solve the problem, because the fault lies in how the signal is being processed, not in the sensor itself.

What this means in practice

Unfortunately, without hands-on testing, it's not possible to guarantee which of the two is at fault. From experience:

• A bad PE sensor is common and relatively inexpensive, so it's often the first thing people try.

• A mainboard fault is less common but more expensive, and usually considered only after sensors and wiring are ruled out.

So yes, the PE sensor could be the fix-but it's not the only possible cause.

Error behavior to be aware of

The ET-8550 does not always display a clear numeric error code for phantom paper jams. Instead, the issue presents as:

• Immediate paper jam error on power-up

• No actual paper movement

• Automatic tray ejection

These symptoms still align with sensor or mainboard signal faults, even without a visible code.

Addressing printer issues can be a complicated affair due to the hands-on nature of the problems. As a result, we're not able to provide remote troubleshooting, step-by-step suggestions, or direct repair support. We do offer an in-person evaluation and repair service through our local diagnostic facility, printer repair service (https://bchtechnologies.com/printer-repair-service). Due to high demand, repairs are handled on a first-come, first-served basis, and it may take a few weeks before we can schedule a drop-off. Our services are designed to repair either an entire printer or specific components, with clear guidance on how the process works. That said, we recognize our rates aren't the most economical, so we strongly encourage self-help through online research first. You can start with YouTube or by visiting our channel homepage at BCH Technologies on YouTube (https://youtube.com/@bchtechnologies). Use the search icon next to "About" on the right-hand side of the menu bar to find videos on very specific topics. I receive dozens of questions daily asking about videos for particular issues, and after nine years of creating content, it's difficult to remember every single one-so YouTube's search function is the most efficient approach. You may also find helpful videos from other creators suggested by YouTube.

Thank you again for reaching out and for supporting BCH Technologies. I truly appreciate your patience, and I hope this gives you a clearer picture of what may be causing the phantom paper jam on your ET-8550.