Product review (3 stars): Worked real well for 3.5 years
After that time we started getting the F-35 code. Tried cleaning drain as suggested online.  The next step was to replace the analog pressure sensor, $168 with next day delivery. That fixed the problem, but the price is a ripoff and less than 4 year old washer should not need any repairs.
The part is a small unit with a small electronic circuit with a pressure switch.
I bet their cost is less than $10
1. Remove three screws on the back of the top.
2. Slide the top forward about half an inch and lift off.
3. the switch is mounted on the upper right.
4. Remove it from the side and slide the black cover up to make it easier to unplug the connector,
5. Remove hose.
6. Plug in new sensor and connect hose.
7. slide cover down and install unit.
I see now that the part is available for less from some suppliers on Amazon.