What does the 'F21' error code mean and how do I fix it?

The F21 error code indicates a drain problem. Select PAUSE/CANCEL twice to cancel the cycle and unplug the washer. Check if the drain hose is kinked, frozen, or clogged, and verify the drain hose is not more than 96 inches (2.4 m) above the floor. After checking these items, plug the washer back in, re-select the cycle and press START. If the problem remains, call for service. (Page 20)