Whirlpool washer duet LF error code

My washer recently started giving me an LF error code.
The washer works perfectly fine on HOT. But if you put it on cold or warm you get the LF error code.
I’ve done a bunch of research and tried the following fixes with no luck.

  1. replaced hoses
  2. cleaned inlet valves/screens
  3. replaced cold water inlet valve
  4. reversed hoses. (Just to confirm it’s not the pressure from the house)
  5. cleaned the drain trap (didn’t know there was one, it was scary)
  6. inspected pressure tube for wear, etc. It’s like new.

Any other thoughts on what this could be?
I would rather not keep randomly replacing parts until something works. That gets expensive.