What is error code F21 on a Kenmore elite washer its an H E T 3 Steam ?

The F21 error on this line of washers is the machines way of saying the water took to long to drain from the tub. This could be a problem with one of the washer parts including the drain pump itself, how the drain hose enters the stand pipe, or maybe even something is stuck somewhere in the drain system and is preventing the water from flowing properly. Not quite an emergency, but it is an indication of a problem and a problem that can lead to something bigger if not looked into. Lint buildup may also cause this problem.