Scott L Warrenton , VA January 15, 2022 Appliance: Whirlpool Washer WFW9400SU02 Whirlpool Washer Wfw9400su02: F20 and f21 Error codes. How to replace Hose. Took the line off the water level sensor and blew air through as it was clogged. 1 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: Less than 15 minutes