Epson DTG Printer 51H, 52H, and 71H Error Fix: Understanding AGP Error Causes and Solutions

Question:
I recently replaced the cap station and printhead on my Epson DTG printer, and now I'm getting an AGP error. The printer's carriage still moves up and down as expected, but the error remains. Could this be caused by a loose cable or something else?

Answer:

Let's go over your question about the AGP error on your Epson DTG printer after replacing the cap station and printhead. The AGP (Auto Gap Position) error-sometimes displayed as Error 51H, 52H, or 71H-indicates that the printer's carriage height or head position sensor isn't reading correctly during startup or printing. Essentially, the printer cannot correctly determine the vertical position of the printhead relative to the platen.

Here are the most common causes and troubleshooting steps for this issue:

1. Printhead Carriage Cable Connection

   • After replacing the printhead, it's easy for one of the ribbon cables (especially the thin head data cables) to become misaligned or not fully seated. Even a slight offset in the cable's insertion can cause the sensor or mainboard to misread signals.

   • Carefully recheck all cables leading to the printhead carriage, the encoder sensor, and the cap station motor. Ensure they're inserted straight and fully locked into place.

2. Encoder Strip or Sensor Contamination

   • The encoder strip (the transparent plastic strip behind the carriage) helps the printer track head movement. If ink, oil, or dust has built up on it during the repair process, the printer may misinterpret the carriage's position and throw an AGP error.

   • Clean the encoder strip gently using a lint-free cloth and a small amount of isopropyl alcohol. Avoid touching the strip with your bare fingers, as oils can cause additional misreads.

3. Cap Station Alignment

   • Since you replaced the cap station, it's possible that it's slightly misaligned vertically or horizontally. The AGP system depends on the cap station to seal correctly against the printhead during initialization. If the printer detects too much resistance or a gap that's too small, it can trigger the AGP error.

   • Verify that the cap station is level and properly seated. The capping unit should rise evenly to meet the printhead surface without excessive pressure.

4. Height Detection Sensor or Motor Issue

   • The DTG models use a small height detection sensor-usually an optical or mechanical switch-that tells the system when the carriage is at the correct height. If this sensor is dirty, blocked, or damaged, it can cause Error 51H or 52H.

   • Clean the sensor area with compressed air or a soft brush, and check if the sensor connector is firmly attached.

5. Mainboard or Firmware Communication Fault

   • If all physical connections appear fine, the issue might stem from firmware miscommunication after a component change. Disconnect the printer from power for at least five minutes to allow capacitors to discharge, then reconnect and restart.

   • In rare cases, a mainboard driver IC or the AGP control circuit could be faulty, especially if power irregularities occurred during replacement.

If the printer moves freely and doesn't make grinding or collision noises, the issue is likely with signal interpretation rather than a mechanical jam. Double-check cable seating and cap station alignment first-these are by far the most common culprits after maintenance work.

Addressing printer issues can be a complicated affair due to the hands-on nature of the problems. Therefore, we're unable to provide remote troubleshooting, suggestions, or direct repair support. However, we offer in-person diagnostic and repair services through our local printer repair facility (https://bchtechnologies.com/printer-repair-service). Because of high demand, we operate on a first-come, first-served basis, so it may take a few weeks before we can evaluate your printer. Our services cover complete printer repairs or specific component replacements, with step-by-step instructions to guide the process.

That said, we fully understand that professional repairs can be expensive, so we always encourage DIY troubleshooting through reliable resources. You can start by searching for related tutorials on our BCH Technologies YouTube channel (https://youtube.com/@bchtechnologies). Use the search icon beside "About" on the right-hand side of the menu bar to locate videos on "Epson DTG AGP error" or similar topics. We've posted hundreds of detailed videos over the years, and searching directly will help you find the most relevant one.

Thank you again for reaching out and for being part of the BCH Technologies community. Your thoughtful questions and continued support inspire us to keep creating the most informative and practical printer repair resources possible.