Diagnosis
Support Code 1688 indicates that the ink absorber is almost full. Inside your Canon PIXMA TR4720, there are physical sponges designed to collect excess ink generated during print head cleaning cycles and nozzle checks. The printer tracks the volume of ink sent to these pads via an internal counter; once that counter reaches a specific threshold, the 1688 warning triggers to prevent ink from overflowing onto your desk.
How to Fix It
Since this is a maintenance warning and not a critical failure, you can typically continue printing for a short period. However, to clear the alert and maintain the device, follow these steps:
- Perform a Hard Reset: Turn the printer off, unplug the power cord for 60 seconds, and restart. This sometimes clears temporary glitches, though the counter usually persists.
- Check Ink Levels: Ensure your cartridges are seated correctly and have ink, as low ink levels during a cleaning cycle can sometimes trigger absorber warnings prematurely.
- Clear the Warning: On many TR-series models, you can acknowledge the message by pressing the "Stop" or "Resume" button to bypass the alert and continue printing until the absorber is completely full (at which point the printer will lock entirely).
If That Didn't Work
If the printer has transitioned from a warning to a complete lockout (Support Code 5B00 or similar), the internal counter must be reset.
- Service Tool Software: You will need a Canon Service Tool (ST) software utility to reset the waste ink counter to zero. This requires a PC connection via USB.
- Physical Replacement: If you reset the software without replacing the physical sponges, the ink will eventually leak out of the bottom of the chassis. If you are comfortable opening the device, you can replace the absorbent pads or install an external waste ink bottle (waste ink diverter).
- Professional Service: If you are not comfortable with hardware modification, send the unit to an authorized Canon technician for a physical pad replacement and a factory counter reset.
Heads Up
Do not simply reset the software counter and ignore the hardware. If the pads are physically saturated, ink will leak from the bottom of the printer, which can damage your furniture and potentially cause a short circuit on the printer's main logic board.