my ts6520 just shows 'check ink' and won't print even though the cartridges are full, what gives?

Diagnosis

The "Check Ink" error on the Canon PIXMA TS6520 is rarely about the actual volume of ink remaining in the reservoir; rather, it is a communication failure between the cartridge's gold contact points and the printer's internal sensor array. This model utilizes a chip-based monitoring system that reads electrical resistance to estimate ink levels. When a layer of oxidized ink, dust, or a microscopic film of oil builds up on these contacts, the circuit is broken, triggering a "false empty" or "ink exhausted" state that locks the print head to prevent permanent damage from printing "dry."

Furthermore, this specific error often occurs after using third-party remanufactured cartridges or if the printer has been idle for several weeks. In these cases, the printer's firmware fails to recognize the chip's unique ID or detects a discrepancy in the voltage return, leading the OLED display to signal an error even if the tanks are physically full. You can confirm this by attempting to print a nozzle check pattern; if the printer refuses to move the carriage at all, it is a logic-level communication error rather than a physical clog.

How to Fix It

To resolve the communication error and clear the "Check Ink" message, follow these precise steps to reset the hardware interface:

1. Power down the printer completely and unplug the power cord from the wall outlet to discharge any residual electricity in the capacitors.
2. Open the scanning unit/cover to expose the ink carriage. Wait for the carriage to slide to the center. If it doesn't move, manually slide it to the replacement position.
3. Carefully remove all four ink cartridges (C, M, Y, and BK) by pushing down on the tabs.
4. Inspect the gold-plated contact pads on the back of each cartridge. Use a lint-free microfiber cloth dipped in a small amount of 90% isopropyl alcohol or distilled water. Gently wipe the contacts in a single direction to remove oxidation or ink residue.
5. Look inside the printer's cartridge slots. Locate the small gold spring-pins that make contact with the cartridges. Use a dry cotton swab to gently clean these pins, ensuring no fibers are left behind.
6. Reinsert the cartridges. You must hear a distinct "click" for each one. If the cartridge is not seated perfectly flush, the pins will not engage, and the error will persist.
7. Close the cover and plug the printer back into the wall.
8. When the "Check Ink" message reappears on the OLED screen, press and hold the Stop/Reset button (the red triangle icon) for exactly 5 to 10 seconds. This overrides the ink level monitor and forces the printer to ignore the low-ink warning.

If That Didn't Work

• Perform a Hard Logic Reset: Turn the printer on, then unplug the power cord from the back of the machine while it is still running. Wait 60 seconds. Plug it back in and immediately hold the Stop button while powering on. This clears the volatile memory cache where the ink error is stored.
• Update Firmware via Canon PRINT App: Sometimes the TS6520 encounters a "chip mismatch" error due to outdated firmware. Use the Canon PRINT Inkjet/SELPHY app on your smartphone to check for a firmware update. Updating the internal OS can resolve compatibility issues with newer batches of ink cartridges.
• Isolate the Faulty Cartridge: Remove all cartridges except for the Black (BK). If the printer allows you to enter the menu, the BK is fine. Add the Cyan (C) and repeat. The moment the "Check Ink" error returns, you have identified the specific cartridge with the defective chip. Replace that single unit.
• Clean the Encoder Strip: If the printer thinks the ink is low because the carriage isn't reaching the "home" position correctly, locate the thin, clear plastic strip (encoder strip) running across the width of the printer. Gently wipe it with a dry cloth. A smudge of grease here can confuse the printer's positioning sensors, triggering generic ink errors.

Heads Up

• Avoid Tape: Never place adhesive tape over the ink chips to "trick" the printer; this can permanently bend the contact pins in the carriage, requiring a full print head replacement.
• Ink Quality: Using non-genuine ink can lead to more frequent "Check Ink" errors. If using third-party tanks, always keep a spare set on hand as chip failures are more common in remanufactured units.
• Prevent Drying: To prevent the contacts from oxidizing, print at least one full-color page every week. This keeps the print head moist and ensures the electrical contacts remain active.
• Power Cycle: Always use a surge protector. Power spikes can occasionally corrupt the ink level data stored in the printer's NVRAM, leading to phantom "empty" readings.