Robot vacuum shows E4 and stops, often after bumping into furniture or when starting near an obstacle.

Safety first: Power OFF the robot before manipulating the bumper.

• Step 1 – Free the bumper: Press the front bumper in and release it several times. It should move freely and spring back evenly on both sides. If it feels stuck, inspect for jammed debris along the bumper edges and remove it.
• Step 2 – Clean sensors: Wipe the front IR sensor windows (usually dark plastic windows on the bumper) with a soft, dry cloth. Avoid using harsh chemicals.
• Step 3 – Visual inspection: Check that the bumper is not warped or misaligned from an impact. Ensure both bumper springs are in place and not broken.
• Step 4 – Check switches/cable: Remove the front cover or top cover (depending on model) to access the bumper microswitches or IR board. Confirm the sensor cable is firmly connected to the mainboard and that the switches click when the bumper is pressed.
• Step 5 – Replace bumper sensor assembly: If the bumper does not register presses or the IR board is damaged, replace the Medion bumper sensor assembly or IR collision sensor board.