Washer-dryer attempts to drain but pump hums loudly or stops, then E21 appears on the display.

Safety: Disconnect power and prepare for water spillage.

• Clear pump housing: Remove the pump filter and inspect the pump cavity with a flashlight. Remove bra wires, coins, or fabric pieces.
• Inspect sump hose: Access the large black hose from tub to pump. Remove the clamp and check for socks or debris lodged inside. Clean thoroughly and refit with a secure clamp.
• Check impeller condition: If the impeller blades are loose, broken, or wobble on the shaft, replace the AEG drain pump assembly.
• Allow cooling: If the pump overheated due to blockage, let it cool for 30 minutes before retesting. Persistent humming without rotation indicates replacement is needed.

After reassembly, run a drain/spin program to confirm normal operation.