Epson Paper Jam Error With No Paper: PE Sensor vs. PW Sensor and Other Possible Causes

Question

My printer keeps displaying a paper-jam message even though I cannot find any paper stuck inside. After watching BCH Technologies videos on YouTube, I am wondering whether the problem could be the PE sensor or the PW sensor, but I am not sure which one would be responsible.

How can I determine whether I need a PE sensor, a PW sensor, or something else? Also, if I purchase the wrong part, can I return it?

Answer

A paper-jam message when there is no visible paper jam does not automatically mean that either the PE sensor or PW sensor has failed. This is particularly important with Epson inkjet printers, including models such as the ET-8550.

In many Epson printers, "paper jam" is essentially a generic mechanical error message. The printer performs a sequence of movements and sensor checks when it powers on, loads paper, prints, or performs maintenance. If one of those expected movements or sensor changes does not happen within the required time, the printer may stop and display a paper-jam message even though there is no paper physically stuck inside.

Therefore, I would not recommend purchasing either sensor based only on the words "paper jam."

PE Sensor Problems

PE generally refers to the Paper End or Paper Entry sensor, depending on the printer design and terminology being used.

The PE sensor helps the printer determine whether paper has entered or passed a specific position in the paper path. It normally works together with a small mechanical flag or lever. As paper moves through the printer, the flag changes position and the optical sensor detects that change.

Possible PE-related problems include:

• Dust or paper fibers covering the PE sensor

• Ink contamination around the sensor

• A stuck PE sensor flag

• A broken PE flag

• A missing or disconnected return spring

• A flag that does not return to its home position

• A physically damaged PE sensor

• A loose PE sensor connector

• A damaged FFC or wiring harness

• A cable that is not fully inserted

• A damaged connector

• A mainboard circuit that is no longer correctly reading the PE signal

One important point is that sometimes the sensor itself is perfectly good. The problem may simply be the little plastic flag that activates it. If that flag is stuck, broken, incorrectly installed, or missing its spring, replacing the electronic sensor will not solve the problem.

PW Sensor Problems

PW normally refers to the Paper Width sensor.

On many Epson printers, the PW sensor is associated with the printhead carriage and looks downward toward the platen or paper area. It may be used during paper detection, position checking, edge detection, or other initialization and printing functions.

Possible PW-related problems include:

• Ink mist covering the PW sensor

• Dust or debris on the optical surface

• A damaged PW sensor

• A loose or damaged PW cable

• Incorrect PW sensor installation

• Contamination on the platen beneath the sensor

• Excessively reflective or unusual material underneath the carriage

• A carriage that cannot move far enough to complete the PW check

• A mainboard problem affecting the PW sensor signal

Therefore, even when the printer appears to have a PW-related detection problem, the PW sensor itself may not actually be defective. If the carriage cannot travel to the location where the PW reading is supposed to occur, the printer can receive an impossible or missing reading and stop with a generic mechanical or paper-jam message.

Actual Paper-Path Problems

Before replacing any electronic component, it is worth recognizing that very small pieces of material can cause this type of problem.

Possible causes include:

• A small torn piece of paper

• Labels or adhesive material

• Tape

• Foreign objects dropped into the rear feeder

• Paper hidden underneath rollers

• Debris inside the duplexer

• Paper caught underneath a guide

• A damaged paper guide

• Incorrectly positioned paper-width guides

• Curled or damp paper

• Paper that is excessively thick or thin

• Too many sheets loaded

• A cassette that is not completely seated

A printer can also have a mechanical obstruction without any paper being involved at all.

Carriage Movement Can Produce a False Paper-Jam Message

This is one of the most important areas to investigate.

The printhead carriage must move through a specific sequence during startup. If it cannot move correctly, the printer may eventually report a paper jam.

Possible causes include:

• The carriage is physically blocked

• The printhead is still locked into the capping station

• The transportation lock is engaged

• The capping station does not release

• Dried ink has caused the printhead to stick to the cap

• The carriage rail is dirty

• The rail has insufficient lubrication

• A carriage bearing or bushing is binding

• The carriage belt is damaged

• The carriage belt is loose

• The CR motor is defective

• A cable is interfering with carriage travel

• An ink tube is interfering with carriage movement

• CIS tubing is too short or incorrectly routed

• A drag chain is binding on a converted printer

For example, if an Epson ET-8550 turns on, attempts to move the printhead only a short distance several times, and then reports a paper jam, I would be much more interested in what is preventing the carriage and maintenance mechanism from completing their initialization than I would be in immediately replacing a PE or PW sensor.

CR Encoder Problems

The carriage encoder system tells the printer where the printhead carriage is located.

A motor can physically move the carriage while the printer's electronics believe that the carriage is not moving correctly. When that happens, the firmware can stop the printer with a seemingly unrelated mechanical error.

Possible causes include:

• Dirty CR encoder strip

• Ink mist on the encoder strip

• Grease on the encoder strip

• Scratched encoder markings

• Damaged encoder strip

• Encoder strip installed incorrectly

• Encoder strip outside the carriage sensor slot

• Disconnected tension spring

• Dirty carriage encoder sensor

• Defective encoder sensor

The encoder strip should be handled very carefully because contamination or damage can create positioning errors even when the carriage appears to move normally.

Capping Station or Maintenance Station Problems

The capping station is another common cause of what customers often describe as a "fake paper jam."

The maintenance station must cap, release, wipe, and service the printhead while interacting mechanically with the printer's drive system. If it cannot return to its expected position, the startup sequence can fail.

Possible problems include:

• Capping station stuck

• Cap slider stuck

• Wiper stuck

• Pump mechanism jammed

• Purge gears incorrectly timed

• Broken capping-station gear

• Stripped gear teeth

• Gear slipping on its shaft

• Transmission gear not engaging

• Change gear not engaging

• Cam mechanism stuck

• Dried ink restricting movement

• Foreign material inside the mechanism

If the printhead cannot disengage from the capping station, the printer may interpret the resulting failure as a carriage, transportation, or paper-jam condition.

PF Motor and Paper-Feed Drive Problems

PF generally refers to the Paper Feed mechanism.

The printer expects the PF drive system to rotate a specific distance and uses encoder feedback to verify the movement.

Potential causes include:

• Defective PF motor

• Disconnected PF motor cable

• Dirty PF encoder disk

• Defective PF encoder sensor

• Cracked encoder disk

• Encoder disk slipping on its shaft

• Loose PF belt

• Broken PF belt

• Damaged PF pulley

• Binding PF shaft

• Cracked drive gear

• Slipping gear

• Gear moved sideways on its shaft

• Stripped gear teeth

• Transmission mechanism not engaging

Again, the printer may display "paper jam" because it commanded the PF motor to move and did not receive the encoder response it expected.

Pickup Roller Problems

Paper pickup failures can also trigger jam-related messages.

Possible issues include:

• Pickup roller worn smooth

• Dirty pickup roller

• Pickup roller not rotating

• Broken pickup shaft

• Missing pickup spring

• Weak or disconnected pickup-arm spring

• Pickup mechanism incorrectly timed

• Slipping clutch

• Damaged one-way bearing

• Roller installed incorrectly

• Paper cassette not fully seated

Sometimes the printer is expecting a sheet of paper to reach the PE sensor within a particular time. If the pickup mechanism never delivers the sheet, the firmware may interpret the missing sensor transition as a feed or jam problem.

Paper-Lift and LD Mechanism Problems

On printers with more complicated paper-handling systems, the loading mechanism itself can be responsible.

Possible causes include:

• LD assembly stuck

• LD cam incorrectly timed

• Damaged LD gear

• Broken LD lever

• Paper lift plate not rising

• Cassette lift mechanism jammed

• Rear hopper mechanism jammed

• Sheet feeder incorrectly timed

• Paper guide not returning to home position

The important diagnostic distinction is whether the sensor is failing or whether the mechanical system is simply failing to move something into the position that the sensor expects.

Duplexer Problems

If the printer includes a duplex unit, problems in that assembly can also generate a paper-jam message.

Possible causes include:

• Duplexer not completely installed

• Jammed duplexer gears

• Small piece of paper inside the duplexer

• Stuck duplex sensor flag

• Broken sensor flag

• Duplex rollers not rotating

• Incorrect gear timing

• Drive failure

• Foreign material in the duplex path

Removing and reinstalling parts can also change gear timing if the mechanism is rotated while disassembled.

Rear Feeder Problems

The rear feeder contains several components that can produce misleading paper-jam symptoms.

These include:

• Stuck rear-feed sensor flag

• Incorrectly timed rear-feed rollers

• Cam or half-moon roller out of position

• Damaged rear-feeder gear

• Hopper not returning to its home position

• Jammed rear-feed guide

• Dirty sensor

• Foreign object dropped into the feeder

A pen cap, screw, paper clip, piece of plastic, or other small object can sometimes create a mechanical problem that is difficult to see from above.

Output Mechanism Problems

The paper exit area should not be overlooked either.

Possible causes include:

• Jammed output mechanism

• Output tray unable to extend or retract

• Damaged tray motor or gear

• Output roller jammed

• Stuck paper-exit sensor

• Broken exit-sensor flag

• Foreign object near the output rollers

On printers with motorized output trays, a failure to initialize that system can occur before any printing takes place.

Timing Problems After a Repair

If the printer was recently disassembled, timing and reassembly problems become especially important.

Examples include:

• Gear installed one tooth out of position

• Cam installed in the wrong home position

• PF shaft rotated while gears were removed

• Capping station installed out of phase

• Sheet feeder incorrectly timed

• Duplex system incorrectly timed

• Transmission slider installed incorrectly

• Change gear installed incorrectly

• Spring attached to the wrong location

• Sensor flag installed on the wrong side of a lever

These problems are particularly deceptive because all of the individual parts can appear intact.

Broken or Displaced Gears

A gear does not have to be completely destroyed to cause a problem.

Possible failures include:

• Cracked gear

• Split gear hub

• Gear slipping around a shaft

• Missing retaining clip

• Missing E-clip

• Gear shifted sideways

• Partially stripped teeth

• Gear installed upside down

• Gear not completely seated

A cracked gear may look normal while the printer is off but begin slipping when the motor applies torque.

FFC and Connector Problems

FFC cables are another important area because many sensors and motors depend on them.

Possible problems include:

• Loose FFC

• FFC inserted crooked

• FFC installed upside down

• Damaged conductive trace

• Torn cable

• Corroded contacts

• Ink inside a connector

• Broken connector latch

• Folded contact

• Cable not completely inserted

• Cable pinched during reassembly

A sensor can be perfectly functional but effectively invisible to the mainboard if its signal cannot travel through the cable.

Mainboard Problems

Mainboard failures are less common than basic mechanical problems, but they are absolutely possible.

Examples include:

• Failed sensor input circuit

• Motor-driver failure

• Blown fuse

• Damaged MOSFET or transistor

• Ink corrosion

• Shorted connector

• Failure to read an encoder signal

• Failure to drive the CR or PF motor

• Damaged voltage rail

• Electronic failure causing impossible sensor readings

In this situation, replacing a PE or PW sensor would not solve the underlying problem.

Printhead or Electrical Problems

Occasionally, an electrical failure during startup can result in a misleading mechanical message.

Possible problems include:

• Shorted printhead

• Ink-contaminated printhead FFC

• Burned printhead connector

• Ink on cable contacts

• Damaged head cable

• Failed head-driver circuitry

• Mainboard protection circuitry shutting down a voltage rail

This is another reason that we try not to diagnose a paper-jam message based only on the wording shown on the display.

Ink Contamination

Ink can create both electrical and mechanical failures.

For example, ink may contaminate:

• PW sensor

• Encoder strip

• PF encoder disk

• FFC connectors

• Optical sensors

• Sensor flags

• Mechanical gears

• Maintenance-station components

Dried ink can make a sensor flag sticky or physically lock a mechanism that should move freely.

Modified and DTF-Converted Printers

If the printer has been converted or modified, additional possibilities need to be considered.

These include:

• CIS tubing pulling on the carriage

• Tubing routed across the carriage path

• White-ink tubes that are too stiff

• Drag chain binding

• Added brackets interfering with moving parts

• Modified waste tubing interfering with gears

• Cable tension caused by relocated electronics

• Modified capping system incorrectly aligned

• Removed paper-feed components producing unexpected sensor states

• Aftermarket control boards or bypass systems malfunctioning

A modification can therefore produce a paper-jam message even when the original Epson paper-handling components are functioning correctly.

Incorrect Assembly Can Also Cause the Error

Even seemingly minor assembly mistakes can interfere with movement.

Examples include:

• Long screw installed where a short screw belongs

• Screw protruding into a moving mechanism

• Cable trapped underneath a frame

• Cover pressing against a gear

• Spring omitted during reassembly

• Washer or spacer missing

• Sensor bracket installed backward

• Retaining ring omitted

• Shaft not fully seated

These are particularly worth considering if the error began immediately after another repair.

Watch What the Printer Does Before the Error

For diagnosis, the movement immediately before the error is often more informative than the words "paper jam."

During startup, a printer may need to:

• Unlock the carriage

• Release the printhead from the capping station

• Move the carriage

• Find the carriage home position

• Rotate the PF shaft

• Initialize the capping station

• Initialize the paper-feed mechanism

• Check the PE sensor

• Check the PW sensor

• Verify encoder feedback

• Initialize the duplexer

• Initialize the output mechanism

If one operation does not finish correctly, the printer may eventually display a generic paper-jam message.

For example, if an ET-8550 powers on, the carriage attempts to move left only an inch or so several times, and then the printer stops with a jam message, I would investigate the carriage release system, capping station, CR encoder feedback, and related drive mechanisms before automatically purchasing either a PE or PW sensor.

On the other hand, if the printer initializes normally and only reports the problem after attempting to pick up a sheet, the PE sensor, pickup system, paper-feed drive, sensor flag, or related mechanisms become more relevant.

That distinction is why I would not want to guess whether you need a PE sensor or a PW sensor without knowing the exact printer model and performing proper diagnosis.

What Happens If You Purchase the Wrong Part?

If you purchase a part from us and later determine that it was not the component causing the problem, we do accept eligible returns within 30 days.

There is a $5 per-item restocking fee, and the original shipping cost is not refundable. Therefore, if you are unsure which part has failed, it is usually better to spend additional time diagnosing the printer before ordering several possible components.

Replacing parts based solely on a generic paper-jam message can become expensive very quickly because PE and PW sensors are only two possibilities among many.

Addressing printer problems can be complicated because so much of the diagnosis depends on physically observing and testing the machine. For that reason, we are not able to provide remote troubleshooting, repair suggestions, or individualized repair support. We do offer an in-person printer evaluation and repair service [https://bchtechnologies.com/printer-repair-service] through our local diagnostic facility. Because demand is high, the service operates on a first-come, first-served basis, and it may take several weeks before we can accommodate a printer for drop-off. Our service options are structured around either complete-printer repair or evaluation and repair of specific components, with instructions explaining how to proceed. We also recognize that our repair rates may not be the most economical option for every situation, so we strongly encourage customers who are comfortable working on their own equipment to use online resources for self-help. A good starting point is YouTube and the BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies]. On our channel homepage, you can use the search icon located near the "About" section to search for your printer model, error message, sensor, or mechanical problem. We receive dozens of questions asking whether we have made videos about particular issues, and after producing repair videos for more than nine years, it is difficult to remember every topic we have covered. Using YouTube's search function is usually the fastest way to locate the relevant material, and YouTube may also recommend useful videos from other repair channels.

Thank you again for contacting BCH Technologies and for taking the time to watch and support our videos. We appreciate your interest in understanding the problem before purchasing parts, because careful diagnosis is the best way to avoid replacing components that are still functioning correctly. We hope this information gives you a clearer understanding of why a paper-jam message does not necessarily point directly to the PE or PW sensor.