Robot mower shows E04 and refuses to start; message may indicate boundary wire or signal error.

Safety: Turn the mower OFF and unplug the charging dock before working on the boundary system.

• Check dock boundary terminals: At the charging station, verify that both ends of the boundary wire are firmly clamped into the boundary terminals. Tighten any loose screws or clips.
• Inspect for visible breaks: Walk the perimeter and look for cut or exposed wire, especially where recent gardening, edging, or pet activity occurred. Repair breaks using Yarbo‑compatible waterproof boundary wire connectors.
• Short loop test: Disconnect the yard boundary wire from the dock and connect a short 2–3 m test loop of wire directly to the dock terminals. If E04 clears and the mower recognizes the loop, the yard wire is damaged somewhere in the lawn.
• Check dock signal LED: Many Yarbo docks have a boundary signal indicator. If it is off or red even with a short loop, the boundary signal generator module inside the dock may be faulty and the dock assembly should be replaced.