Robot announces E4 and stops, often near stairs or dark rugs

Safety: Power the robot OFF.

• Locate cliff sensors: These are the downward-facing infrared sensors along the front underside of the robot.
• Clean sensors: Use a soft, dry microfiber cloth to gently wipe each sensor window. For stubborn grime, lightly dampen the cloth with water (no chemicals) and dry immediately.
• Check environment: Avoid running the robot in direct sunlight on very shiny or black floors, which can confuse sensors.
• Reboot: Turn the robot back on, or perform a full power cycle (switch off, wait 30 seconds, switch on) and test again.

If E4 continues after cleaning and rebooting, the cliff sensor module may be faulty and require replacement.