Robomow displays E4 and stops mowing, often when encountering obstacles or on uneven terrain.

Safety first: Switch the mower OFF and wait for all movement to stop before touching the bumper area.

• Inspect bumper movement: Gently press and release the front bumper across its width. It should move freely and return to its original position. If it feels stuck, look for trapped branches, stones, or packed grass and remove them.
• Clean bumper gap: Use compressed air or a soft brush to clear debris from the gap between the bumper and chassis.
• Check bumper springs: From underneath or by slightly lifting the front (with power OFF), verify that the bumper springs are intact and not broken or dislodged.
• Reset the mower: After freeing the bumper, power the mower ON and clear the error. Start a manual mow and gently press the bumper to confirm it stops and then resumes correctly.
• If E4 persists: The bumper switch strip or sensor wiring may be damaged. This requires removing the front cover and testing continuity of the bumper sensor; if you are not experienced with electronics, have a Robomow service center replace the bumper sensor assembly.