Robot vacuum stops near stairs or dark carpets and shows C04.

Safety first: Turn the robot off and place it upside down on a soft surface.

• Locate cliff sensors: These are usually small downward‑facing IR sensors along the front underside of the robot.
• Clean sensors: Use a soft, dry cloth or cotton swab to gently clean each sensor window. Do not use harsh chemicals. If needed, slightly dampen the cloth with water and dry thoroughly.
• Check for physical damage: Inspect the sensor windows for cracks or heavy scratches. If damaged, the sensor board may need replacement.
• Test on flat surface: After cleaning, power on the robot and test it on a flat, light‑colored floor away from stairs. If C04 still appears, the cliff sensor PCB or wiring is likely faulty and should be replaced.