The F-28 error code means ,,The communication between the Central Control Unit (CCU) and the Motor Control Unit (MCU) cannot be sent correctly.
1. Unplug washer or disconnect power.
2. Check wire harness connections to the MCU, the motor, and Central Control Unit (CCU).
– Check connections of the CCU board within the housing.
– Make sure all grounding switches are engaged.
3. Check that the serial harness at the MCU is not mounted upside down. The wires should be to the left when facing the MCU connectors.
4. Check the drive system for any worn or failed components.
5. Plug in washer or reconnect power.
If you still get the F-28 the tech sheet says to replace the CCU board.
You could have a loose wire or the CCU is starting to go bad.