Epson ET-M3170 Rear Paper Feed Error: PF Sensor Diagnosis and Replacement Options

Question

I have an Epson ET-M3170 monochrome printer that keeps showing an error saying the paper is loaded the wrong way in the rear paper feed. This started shortly after I purchased the printer, and there were no paper jams or other obvious problems before the error appeared. I suspect the printer may need a new PF sensor. Can BCH Technologies help with this issue?

Answer

For your Epson ET-M3170, the error saying that the paper is loaded the wrong way in the rear paper feed is usually related to the printer's paper feed detection system. In Epson printers, this can involve several parts, including the PF sensor, paper path sensor flag, rear paper feed sensor, encoder-related components, or even a mechanical issue in the paper pickup area.

Since you mentioned that the problem started shortly after purchase and was not caused by a jam, a faulty or misaligned PF sensor is definitely one possibility. However, it is not the only possibility. The printer may be detecting paper incorrectly because the sensor is bad, the sensor flag is stuck, the paper guide is not triggering the sensor properly, or the rear feed mechanism is not moving paper at the expected angle or timing.

The PF sensor, which stands for paper feed sensor, helps the printer detect whether paper is present and whether the paper is moving through the printer correctly. If the sensor does not detect the paper at the right time, or if it detects paper when it should not, the printer may report a paper loading error even when the paper appears to be loaded properly.

In your case, the error message about the paper being loaded the wrong way in the rear paper feed could be caused by one or more of the following:

1. Faulty PF sensor
   The sensor itself may be defective. If the printer was almost new when the issue started, it could have been a weak sensor from the beginning.

2. Stuck or damaged sensor flag
   Many Epson paper sensors use a small plastic lever or flag that moves when paper passes through. If this flag is stuck, bent, missing, or not returning to its normal position, the printer may think the paper is incorrectly loaded.

3. Dirty sensor area
   Paper dust, ink mist, debris, or a small scrap of paper can interfere with the sensor. Even if there was no obvious jam, a tiny piece of paper or dust buildup can cause a false reading.

4. Rear paper feed alignment problem
   If the rear tray guides are too loose, too tight, or the paper is not seated correctly, the paper may enter the printer at a slight angle. The printer may then report that the paper is loaded incorrectly.

5. Paper pickup roller issue
   If the pickup roller slips or does not pull the paper evenly, the printer may misread the paper's position. This can look like a sensor error even when the sensor is working.

6. Main board or cable issue
   The PF sensor connects to the printer's logic board through a cable or connector. If the sensor cable is loose, damaged, oxidized, or not seated correctly, the printer may receive an incorrect signal.

As for whether we can help with the part, the answer is: possibly, but we would need your help identifying the exact sensor first. We do not have complete part data for every Epson model and every possible sensor variation. Epson often uses different sensor boards or sub-assemblies across similar printer models, and the exact part can vary depending on the production batch or region.

The best way to proceed is for you to remove the PF sensor from the printer and check the markings printed on the sensor board. These boards usually have an identification code printed directly on them. It may look something like "XXX-SUB B" or a code similar to "CG22ENCB." That is only an example, but the actual board should have some kind of printed part identifier. Once you remove the sensor and provide the code printed on it, we can compare it with parts we may have or help determine whether it matches a known Epson sensor.

When inspecting the PF sensor, please also check the following:

• Look for a small printed code on the sensor board.

• Check whether the sensor has a moving flag or lever.

• Make sure the flag moves freely and returns to its original position.

• Inspect the cable and connector for damage.

• Take clear pictures of the front and back of the sensor board.

• Take a picture of where the sensor was installed before removing it.

• Check whether the surrounding paper path has debris, torn paper, or dust.

Before replacing the sensor, it is also worth doing a basic inspection of the rear paper feed area. Remove the paper, unplug the printer, and use a flashlight to look inside the rear feed path. Make sure there are no scraps of paper, labels, dust clumps, or foreign objects. Also inspect the paper guides and pickup roller. If the roller is not gripping evenly, the printer may feed paper at an angle and trigger the rear paper feed error.

If the printer is still under warranty, I would also suggest checking with Epson before disassembling it. Since the issue started shortly after purchase, Epson may treat it as a warranty-related defect. Opening the printer or replacing internal parts yourself may affect warranty coverage, depending on Epson's policy and your region.

If you decide to repair it yourself, the most important step is identifying the exact PF sensor. Please do not order a sensor based only on the printer model number unless the seller confirms that it matches the sensor board code. For these Epson parts, the board marking is often more reliable than the printer model alone.

Addressing printer issues can be a complicated affair because many of these problems require hands-on inspection. For that reason, we are not able to provide remote troubleshooting, detailed repair guidance, or live support for printer repairs. However, we do offer an in-person evaluation and repair service through our local diagnostic facility, BCH Technologies Printer Repair Service [https://bchtechnologies.com/printer-repair-service]. Due to high demand, we operate on a first-come, first-served basis, so it may take a few weeks before we can schedule your printer for drop-off. Our services are structured to repair either the whole printer or specific parts, with clear instructions on how to proceed. We also understand that our rates may not be the most economical option for every situation, so we highly recommend self-help through online research whenever possible. A good place to start is YouTube or our YouTube channel homepage, BCH Technologies on YouTube [https://youtube.com/@bchtechnologies]. You can use the search icon next to "About" on the right-hand side of the menu bar to look for videos on your specific issue. I receive dozens of questions every day asking for videos on specific topics, and after creating videos for the past nine years, it is difficult to remember every single one. YouTube's search function will usually be the most efficient way to locate related videos, and it may also suggest helpful videos from other channels.

Thank you again for reaching out to us. If you choose to remove the PF sensor, the most helpful next step would be to identify the exact code printed on the sensor board and compare it carefully before replacing the part.