Robot vacuum reports E4 and stops, often near stairs or dark carpets.

Safety: Turn the robot OFF before cleaning sensors. Do not use solvents.

• Step 1 – Locate cliff sensors: On most Lefant robot vacuums, cliff sensors are small dark windows on the underside near the front edge.
• Step 2 – Clean sensor windows: Use a soft, dry microfiber cloth to gently wipe each sensor window. For stubborn dirt, slightly dampen the cloth with water (not alcohol) and wipe again, then dry thoroughly.
• Step 3 – Check for damage or covering: Ensure no stickers, tape, or aftermarket bumpers are blocking the sensors. Inspect for deep scratches or cracks in the sensor windows.
• Step 4 – Test on a bright, flat surface: Place the robot on a light-colored, flat floor away from edges and start a cleaning cycle. Avoid dark carpets or black mats during testing, as some models misread them as cliffs.
• Step 5 – Reset: Power cycle the robot (turn OFF for 30 seconds, then ON) and retry. If your model supports it, perform a factory reset via the app.
• If E4 persists: The cliff sensor board or main PCB may be faulty. Replacement of the cliff sensor module is usually required.