I took the following steps to fix error code "OE" on LG top load washing machine LG WT1101CS:
1) took off rear panel, removed the drain pump and disassembled drain pump (~20 minutes)
2) verified there was no debris in the drain pump impeller
3) verified there was no debris in all 3 drain hoses (tub to pump, pump to the back of the unit, back of the unit to the wall)
4) verified drain pump was working properly (~10 minutes) - hooked it up to 120V power supply and it ran fine
5) used a Digital Multi-Meter (DMM) to check the voltage from the cables that plug into the drain pump (~10 minutes) - did this by running a spin only cycle which kicks on the drain pump circuit immediately - I found that the cable was only providing about 60V instead of the 120V that the pump needs. This means that a capacitor on the front control board was bad. Since the control board is potted, you can't just replace the capacitor, you have to replace the entire board.
6) Bought a new control board (EBR75857902 [AP5681074]), then disassembled the front of the unit to expose the control board (~5-minute job). Swapped out the control board, plugged all the cables back in, and everything works as it should again.