I had the same problem. Mine ended up being a cut in the pressure switch hose. Here's what I would do to troubleshoot:
1) Clean the filter down bottom one more time. Run a basket-clean cycle and make sure that the drain pump is working. If so, then move to step 2.
2) Do a diagnostic test. Here's some graphical instructions on how to do it:
Grab the codes off the t02 error codes test. There is a reference manual for the codes in a plastic envelope behind the bottom access panel on the front of the washer (panel below the door) -- remove the 3 screws then pull out from bottom. Lookup the codes and see what they mean.
Mine was E22 -- which indicates problem with pressure switch.
3) Do the t06 basket test. If it fails, then open up the top of the washer to check the pressure switch and hose:
Twist the pressure switch 90 degrees clockwise toward the spring to release it. Undo the hose clamps and blow down the hose. Blow into the pressure switch to make sure a contact isn't stuck. I took the bottom panel off the washer and disconnected the other end of the pressure tube from the bottom of the tub. Once disassembled, I blocked the end with my finger to see if the hose was punctured -- sure enough it was. I taped it and reassembled. If after repairing and blowing out, if you still have problems, replace the pressure switch ($60 on Amazon).