I finally experienced the F35/SUD error on my Kenmore Elite HE3T steam washer and in my case it was the analog pressure sensor or APS. With the tub empty I was getting about 1.4VDC out when it should have been about .38VDC so the washer thought the water was not draining out so it will shutdown to prevent a water overfill condition. I ended up repairing the APS with a APS repair kit on the site mentioned below. All you need is a low power (25 watt or so) soldering iron.
Another common failure is that the CCU power supply can cause an issue with the APS so it reads incorrect. There is a repair kit for that issue, too.
The F35 and SUD error cause can be figured out and repaired in most cases. It more than likely will be the analog pressure sensor (APS) or the CCU power supply issue. There are repair kits available for both the APS and CCU to try once you figure out which one is the culprit using a low cost volt meter. Save yourself a very expensive service call and check out repairing your machine yourself.
You can take some readings with your volt meter on the CCU or even the APS and determine which one is causing the F35/SUD indication. See www.f35error.com for videos on how to determine if the APS or CCU is causing your error code.