I have a whirlpool duet sport with an error code F21. It is not a blocked drian pipe, and is making a noise with the pump.

Check drain trap for restriction
If the drain time exceeds 8 minutes, the water valves turn off.
This error code is only shown in Diagnostic test.
Possible Causes/Procedure
- Ask the customer how much detergent they are using and if it is HE
detergent. May have too much suds present causing this condition.
- Turn washer ON to verify pump operates; run the drain cycle.
- Check the drain hose and make sure it is not plugged or kinked.
- Unplug washer or disconnect power
- Make sure that wire harness connections at the Drain Pump, Pressure SW,
& CCU (DP2, PR6 cavities) connectors are not broken or with wires detached,
and that connector internal pins are visible.
- Check continuity from the Drain Pump & CCU (DP2 cavity) connectors.
- Check continuity from the Pressure SW & CCU (PR6 cavity) connectors.
- If the continuity diagnosis failed, Main Harness must be replaced.
- Make continuity test to the Pressure SW. See page 8.
- Check the resistance of the motor pump. See page 8.
- Plug in washer or reconnect power.
- Run the drain cycle.
- If the failure continues, unplug washer or disconnect power.
- Check the drain pump filter for foreign objects.
- Disassemble the drain pump from the washer.
- Check that the impeller is not detached from the motor shaft. If the
impeller is detached from the shaft, is broken or has any scratches,
the drain pump must be replaced.
- Plug in washer or reconnect power.
- Verify the unit operation by performing the Diagnostic Test cycle.
See page 5.
- After the diagnostic test has finished, unplug washer or disconnect
power and wait for 15 seconds.