Many important questions have plagued mankind since the dawn of time. Questions such as, "Why am I here?", "Who is God?", and, most importantly, "What causes SUDs and SD error codes in high-efficiency front-load and top-load washers?" Here now to guide us into the truth and understanding of this important epistemological question is Brother Delawaredrew:
Suds errors are often detergent related. It's not so much that the pump doesn't pump suds (although it doesn't) but that the pressure switch can't tell the difference between suds and liquid. So the computer doesn't see an empty tub.
An easy explanation of when computers generate a suds error is that the program has a set time allowed for the drain part of the cycle. For instance many whirlpool front loaders allow 4 minutes. After that time if the cpu has not seen a change in the pressure switch reading the SD or Suds or whatever error is displayed (this is why clogged or bad pumps show Suds) ... some machines will have some sort of suds killing routine that is initiated and some will just stop. If the CPU still doesn't see a change in water level after continued pumping you usually see a long drain code like LD or F01 or F21.
When I see repeat drain errors I first try to tell if it actually is draining at a good rate... if so I will check the pressure hose for clogs by first blowing into it at the switch end. If that is okay test the switch itself (if no fill errors are happening this is less likely) then the wiring. On models with integrated pressure sensors obviously you can skip testing the switch.
About the Cabrio/Bravos/Oasis models - lint, socks and other items sometimes gather at the sump cover and block the pump intake. Also coins and other items can damage the plastic impellors of the pump; decreasing pump rates yet still moving water.
I only get about 30 minutes per call so I have a pretty set method of diagnosis for problems to eliminate common issues. It works for me but we all think differently. In general I go for simplest solution first unless I know that a certain component is likely; like the analog pressure switches and F35 error.
Hope that helps.
Source: Suds error sd