Robot vacuum shows E04 and stops; may spin in place or fail to drive straight.

Safety first: Power off and remove the robot from the dock before disassembly.

• 1. Basic reset: Turn the robot off for 1–2 minutes, then power it back on and retry a cleaning cycle. Sometimes transient encoder errors clear after a reboot.
• 2. Check for wheel drag: Ensure both drive wheels rotate freely and are not rubbing against the chassis or trapped by debris. Clean as needed.
• 3. Inspect underside sensors: Dust buildup near the wheel housings can interfere with encoders. Use compressed air or a soft brush to clean around the wheel motors and any visible sensor openings.
• 4. Internal inspection (advanced): Remove the bottom cover to access the drive motors. On many Electrolux robots, the encoder is integrated into the motor module. Check for loose connectors or damaged wires leading from the motor to the main board.
• 5. Replace defective wheel motor module: If one wheel consistently fails to report speed (robot veers or spins, E04 returns), replace the corresponding Electrolux drive wheel motor assembly which includes the encoder.
• 6. If both wheels test good: The main control board’s encoder circuitry may be faulty. This requires professional service or main PCB replacement.