I'm assuming that the washer is pumping water out at a decent rate, (draining it into a bucket allows you to verify this) it just throws the OE error after it begins draining. If there are no clogs or restrictions and you have installed a new pump, I would suggest you look for crud in the stub going to the pressure switch hose at the bottom of the tub or in the pressure hose. It could also be a bad pressure switch, but I don't ever recall seeing one fail on an LG. The pressure switch checks the water level in the washer and sends a signal to the control board, which reports the water level as a frequency. If you press and hold the Wash/Rinse button and the Delay Wash buttons together, you should see a water level frequency greater than 25 kHz on the display. If it's lower than that, you most likely have a problem with the pressure hose or pressure switch. It could also be a control board issue but check the other things first.