The "F02" error code on a Whirlpool Duet washer is one of many possible fault codes with the appliance. This one occurs when the washer tries to drain water. The fix for this could be to unblock the drain hose, which is easy to do, or the complete pump for the washer may need to be replaced.
When the washer tries to drain water and can't, it will beep twice; then the "F02" error code will appear on the screen. On some models, the error may appear as "F/02." After four minutes, the washer will clear the error, flash "SUDS" for four minutes then return to the "F02" error. Press "Cancel" twice to clear the error code from the screen.
Check your washer's drain hose for any blockage that could prevent the washer from draining. This could be lint, debris or other foreign objects caught inside the hose. Make sure the hose is not pushed back or blocked by the washer itself. If the hose is bent, water cannot pass through it quickly enough. Check the draining vents inside the washer to make sure nothing is blocking them from that part of the washer.
Refer to your Whirlpool Duet manual to find the location of the drain pump filter. This filters out the water and could be clogged. Remove the filter and clean out any debris inside of it. Once cleared, replace the filter and restart the laundry. If the error appears again, then the filter is not the reason for it.
If none of the above methods fixes the draining problem, then you need to replace the water pump on the washer. Contact Whirlpool customer service and have your model number ready. If the washer is still covered under warranty, an authorized service technician will install the new part free of charge. If your washer is no longer under warranty, customer service will provide you with a replacement part and repair instructions.