If it won't drain the water out then I would clean out the pump filter to see if it resolves your issue.
F28 is usually related to the MCU but you need to check ohm's/continuity with Digital Multimeter (available at most Hardware Store's for $10-20) on the MCU before replacing.
Reply with Model# (located on front panel inside the door) so I can find the Service Repair Manual that includes troubleshooting instruction's.
F28 means SERIAL COMMUNICATION ERROR
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.
- Verify that all grounding switches (located inside the lower Front Panel and Rear Panel) are engaged.
3. Check the drive system for any worn or failed components.
4. Plug in washer or reconnect power.
5. Verify CCU operation by running a Diagnostic Test or any cycle.
6. Check the MCU by looking for operations of the drive motor.
7. Check the drive motor for powered rotations.
8. 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.