Robot vacuum shows E4 and stops, often near stairs or dark floor transitions.

Safety first: Power off the robot and flip it over on a soft surface to avoid scratching.

• Locate cliff sensors: Identify the small infrared windows on the underside near the front edge (usually 3–4 sensors).
• Clean sensor windows: Use a soft, dry microfiber cloth to gently wipe each sensor window. For stubborn grime, lightly dampen the cloth with water and dry immediately.
• Check for damage: Inspect the plastic windows for cracks, deep scratches, or cloudiness that could interfere with the infrared beam.
• Test on a light, flat surface: After cleaning, run the robot on a light-colored, flat floor away from stairs to see if the error clears.
• If E4 continues: A cliff sensor module or its wiring may be faulty. Replacing the cliff sensor array typically requires removing the bottom cover and unplugging the sensor harness.