Most likely a failed DRAIN MOTOR, part number 4681EA2001D

Water drains from the tub...

Through the hole at the bottom of the tub (almost never a restriction/blockage will occur here)

Through the black bellows type hose---into the PUMP HOUSING (once-in-a-while a sock may be in this bellows)

From the PUMP HOUSING---through the STRAINER---into the PUMP MOTOR/IMPELLER housing (coins/buttons/pins/bra wire/BBs/lint etc can accumulate in *both* the STRAINER and the IMPELLER area of the PUMP MOTOR).

Drain water is then forced/pushed through the DRAIN HOSE mounted at the top of the PUMP ASSEMBLY. In some cases---rubber-backed bathroom floor mats have disintegrated during the wash cycle and have COMPLETELY plugged the drain system from the entrance to the PUMP HOUSING----to the gray DRAIN HOSE---a solid mass of sandy/rubbery residue.

As the DRAIN HOSE runs from the PUMP HOUSING to the white-plastic (u-shaped) GOOSENECK CONNECTOR (mounted on the rear of the washer)---water reaches the DRAIN STANDPIPE or UTILITUB.

Blockage can occur at the GOOSENECK---and compressed air is most effective at blowing this small connector free of debris.

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<<< I then tried to send it through a quick rinse/spin cycle (19 minutes)>>>

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Try this...

1) Press: POWER Button (wake-up washer)

2) Press "SPIN SPEED" button---set to NO SPIN

3) Push "START/PAUSE" button

Washer will enter DRAIN CYCLE (pump all water from tub---when operating properly) and shut off after one minute.

<<<This pump WAS running BEFORE i took it apart. I remember running it through a cycle and hearing it suck through the filter plug.>>>

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It's not unusual at all to find a DRAIN MOTOR that "runs" but is too slow (or the impeller is loosely spinning) to effectively drain the wash water out.

Verify first---that no other restriction/blockage is preventing drain.

If the DRAIN MOTOR fails to function consistently---replace it.

<<<The full wash cycle with laundry did fail. I had an OE on it>>>

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"OE"====> No Drain---replace DRAIN MOTOR.

LG part number: 4681EA2001D

Appliance Parts Pros part number: AP4437652

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<<<this time there was fabric softener remaining>>>

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This tells us only that the DRAIN MOTOR failed while attempting to pump out water from the Main Wash (did not advance to the *Rinse* portion of the cycle)---dirty wash water remaining in the tub---triggered an "OE" error. Cycle will *not* advance any further.

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<<<is there possibly some other electronics piece not properly running the cycles?>>>

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No.

Additionally---there are no SERVICE BULLETINS either---which would indicate/describe *software* issues.

An intermittent DRAIN MOTOR can give the appearance that something else is causing the "OE" error.

Part link ==> Drain Pump

Source: LG WM2016CW OE error won't pump in rinse mode