Robot mower stops suddenly, display shows E3, blades stop and mower may be stuck against an obstacle.

Safety first: Turn OFF the main power switch and remove the battery connector. Do not work near the blade disc with power connected.

Fix procedure:

• 1. Free the mower: Move the Yard Force mower away from walls, trees, or garden furniture. Restart on open lawn to see if E3 clears.
• 2. Check bumper movement: Press and release the front bumper by hand. It should move freely and spring back. If it feels stuck or gritty, inspect for stones, twigs, or packed grass and clean thoroughly.
• 3. Inspect bumper switches: Remove the front cover (Torx screws) to access the bumper sensor switches or Hall sensors. Check that mounting screws are tight and the actuator tabs align correctly.
• 4. Check wiring: Follow the bumper harness back to the main PCB. Ensure the connector is fully seated and wires are not broken or pinched.
• 5. Test function: With the mower reassembled and on its side (blades disabled and power ON), gently press the bumper and watch the display or LED indicators. The mower should register a collision only when pressed.
• 6. Replace bumper sensor assembly: If the bumper is mechanically fine but E3 persists, replace the bumper sensor assembly or microswitch set with the Yard Force OEM part.

Warning: Do not bypass or short the bumper sensor; this is a critical safety device.