I have a Whirlpool front load washer with the FO1 and EO3 error. This indicates that water is detected by the pressure sensor water level circuit. I realise some patients is needed in my analysis. I hope it helps you address the issue with some valuable insight.
Make some observations. You may smell the inside of the washer. Does it smell damp with sour soap washer residue ? Consider that there is a buildup of scum throughout the washer.
Disconnect the power and remove the rubber connector from the drain port of the machine at the top left. Attach a shop vacuum hose so that it fits over the drain port to remove the residual water and potential build up. reattach the drain hose.
Add two table spoons of a water based degreaser such as Zep Orange Citrus to the bleach section. Add vinegar to the rinse softener section. Add 3 table spoons of CLR to the detergent section. Add 4 table spoons of baking soda to the tumbler.
The degreaser, vinegar, and CLR will clean the dispenser and enter through the water inlet cycle into the cloths tumbler. The baking soda will make the water more hard to have less suds. Vinegar, and degreaser will remove the tendency of suds as well. The CLR generates suds and is recommend to be low volume near 1/8 cup. The CLR will remove calcification of the tubes.
Turn the cycle dial to the self clean mode, or a hot wash cycle, and turn on the machine. The drain pump will run for a short while and start the clean cycle. There is a chance the sensor will still detect a high level condition. If it does, consider leaving it sit till the next day unplugged to allow and suds that may have accumulated in the sensor tubes to settle.
If the sensor error continues, consider repeating the above. Allow the error code and pumping cycle go run for hours if it likes. Shut the door to tolerate the beeping. Each time the washer is going through a cycle of draining the water. Be patient and get through the self clean cycle once and try again a second time repeating the above.
This should allow you to run about 4 loads. After the loads, consider running the same self cleaning cycle. You might have some alarms but be patient as this process will help you observe that the system works under certain conditions.
The error is more likely do to too much soap. Only add Two table spoons of detergent and softener and add a degreaser. As the washer nears the end of it's cycles and pumps water up to the top of washer drain port it needs to push out the water at a rate where enough water left in the tube and runs back down will not trigger the water pressure/level sensor. In fact, in the rinse cycle, the water is drained in stages as new water is introduced. So the sensor detects various levels through the pressure sensor and can trigger a false condition after any one of the drain cycles.
The main reason is that too many bubbles are being generated and too much air is being introduced as the washer attempts to drain the tube. The bubbles lead to false measurement of level and the pump can not drain the bubble upward.
Take off the top section of the washer and observe the cycles and the clear tube.
If the pump is weak or there is too much air getting to the pump area suds will be generated. Certainly, cleaning the trap at the bottom of the washer will be one of the first things. The tubs checked for cracks, and that your tub smell very clean.
These are things I would do before exchanging parts.
I wish you well.