Robot mower displays E3 and stops; often occurs when the mower is on a slope or after bumping into an obstacle.

Safety first: If the mower is on its side or upside down, turn the main power OFF before touching it. Keep hands away from the blade disc.

• Return mower to upright position: Place the mower on a flat, level surface. Wait 30 seconds, then turn power ON and clear the error.
• Check slope conditions: Verify that the area where E3 occurs is within the maximum slope rating of your Kress model (typically around 20–35%). Avoid mowing across steep slopes; adjust the boundary wire to exclude overly steep areas.
• Inspect wheels and chassis: Look for uneven tire wear, missing wheel lugs, or damage that could cause instability. Repair or replace damaged Drive Wheels or Front Caster Assembly.
• Check tilt sensor mounting: With power OFF, open the housing and locate the Tilt / IMU Board. Ensure it is firmly screwed to its bracket and not loose or hanging.
• Persistent E3 on level ground: If the mower shows E3 even when stationary and level, the tilt sensor is likely defective and should be replaced or recalibrated by a service center.