i just refilled all the inks but the printer still says one color is low or empty, is the sensor broken?

Diagnosis

The Epson EcoTank ET-2800 does not utilize physical float sensors or optical sensors inside the ink tanks to determine fluid levels. Instead, it uses a software-based tracking system known as "ink level estimation." The printer calculates how much ink should be remaining based on the number of pages printed, the density of the ink used per page, and the number of head-cleaning cycles performed. Because there is no actual sensor to "detect" the new ink you just poured into the tanks, the printer continues to display the "low ink" or "ink empty" warning based on its internal mathematical counter. This is why the error persists even when the tanks are physically full to the upper line. To resolve this, you must manually override the software counter to tell the printer that the tanks have been replenished.

How to Fix It

To manually reset the ink level indicators and clear the low-ink warning on the ET-2800, follow these precise steps:

1. Ensure the printer is powered on and sitting at the home screen.
2. Locate the Stop button (represented by a red circle with a white triangle) on the physical control panel.
3. Press and hold the Stop button for approximately 5 to 8 seconds. Watch the LCD screen carefully; the ink level icons will shift or a prompt will appear asking if you have refilled the tanks.
4. When the screen asks "Did you refill the ink tanks?", use the arrow buttons to highlight Yes and press the OK button.
5. The printer will then prompt you to select which specific colors were refilled. Use the arrows to highlight the colors you filled (Cyan, Magenta, Yellow, and Black) and press OK for each.
6. Once all refilled colors are confirmed, the printer will reset the internal counters to 100% and the warning light/message will disappear.

If That Didn't Work

• Perform a Hard Power Cycle: If the software reset is unresponsive, turn the printer off and unplug the power cable from the wall outlet. Wait exactly 60 seconds to allow the capacitors on the mainboard to discharge. Plug it back in and attempt the Stop button sequence again.
• Check for "Ink Out" Logic Lock: If the printer has completely locked you out and won't let you access the menu, try initiating a "Nozzle Check" from the Maintenance menu. Sometimes triggering a print command forces the printer to re-evaluate the ink status before it allows the manual reset to take effect.
• Update Firmware via Epson Software Update: Occasionally, a bug in the firmware causes the ink counters to "stick." Download the Epson Software Update utility on your PC or Mac, connect the ET-2800 via USB or Wi-Fi, and check for any pending firmware updates that address ink monitoring logic.
• Check the Ink Valve: Ensure the transport lock (if applicable to your specific regional variant) is set to the "Printing" position. If the printer thinks it is in transport mode, it may ignore ink level resets to prevent air bubbles from entering the lines.

Heads Up

• Never let the tanks run completely dry: Because there are no real sensors, if you wait until the printer tells you it's empty, you may have already sucked air into the print head. This causes "banding" or missing colors that a simple reset won't fix; you would need to run a "Power Cleaning," which consumes a massive amount of ink.
• Fill to the Upper Line: Always fill the tanks up to the top line, but never overfill them. Overfilling can cause ink to leak into the internal chassis or create pressure imbalances that lead to ink blotting on the page.
• Use Genuine Epson 504 Ink: Using third-party inks with different viscosities can trick the software counter into depleting faster than the actual ink is being used, leading to more frequent "low ink" warnings.
• Avoid Frequent Head Cleanings: Every time you run a cleaning cycle, the printer subtracts a significant amount of ink from its internal estimate, even if the physical tank is full. Only clean the heads if you see visible gaps in your printouts.