LG Washer Error Code UE: Run the Service Tests

The Logic Verdict

Ryan from PartsDoctor doesn’t guess when UE pops up—he goes straight into LG’s hidden service mode and runs all seven diagnostic tests back-to-back. Power + Start enters the mode, every light turns on, and each press of Start drives a different load: detergent door, vent blower, soil sensor, drain motor, inlet valve, wash motor, and the vario valve that sends water to the upper (1 uN) or lower (1 Lo) spray arms. If any station fails or the display throws nE, you’ve isolated the piece that’s keeping the wash system out of balance.

What It Means

UE (displayed as uE/UE on LG dishwashers) = the controller can’t keep the wash system balanced between the upper and lower spray zones. The board watches motor RPM, water level, and soil readings during service mode; when one of those readings is missing, the dishwasher stops mid-cycle and flashes UE until you address the failing component.

Common Causes

• Detergent door or vent harness issues. Tests 1–2 prove the dispenser solenoid and vent blower can energize; loose connectors here can flag UE early in the cycle.
• Drain or inlet restrictions. Tests 4–5 show whether the drain motor hits its RPM target and whether the inlet valve can actually feed the tub. Obstructions or bad valves leave water where it shouldn’t be and confuse the load sensors.
• Wash motor or vario valve failures. Tests 6–7 read the circulation motor RPM and verify the diverter swings from 1 uN (upper) to 1 Lo (lower). If the motor can’t spin or the diverter sticks, the board sees an unbalanced load and posts UE.

Step-by-Step Fix

1. Enter service mode. With the dishwasher powered down, press Power and Start together. All panel lights illuminate and the display flashes, confirming you’re in diagnostics.
2. Run Test 1 – Detergent dispenser. Close the detergent lid, shut the door, and press Start. A healthy solenoid snaps the door open; if it doesn’t, inspect the dispenser or control output.
3. Run Test 2 – Vent blower. Press Start again to energize the vent motor and wax assembly. You should hear the fan spin and see the vent open; no movement means the blower or wax motor needs attention.
4. Run Test 3 – Soil sensor. Another tap of Start displays the water-clarity reading. If the numbers don’t change with clean water, clean the sensor window or replace the assembly.
5. Run Tests 4 & 5 – Drain and fill. Press Start twice more: the first activates the drain pump (listen for a steady hum and watch the RPM on the display), the second opens the inlet valve (confirm water pressure is available and don’t leave it filling unattended).
6. Run Test 6 – Wash motor RPM. Press Start again to watch the circulation motor spin. Low or zero RPM indicates a seized pump or wiring fault.
7. Run Test 7 – Vario valve. The final press toggles the diverter. The display should flip from 1 uN (upper spray) to 1 Lo (lower) and settle on 0 Lo when complete. If you see nE or the spray pattern doesn’t change, replace the diverter assembly.
8. Exit diagnostics and repair the failed stage. Press Start one more time to leave service mode, power down, and service the component that didn’t respond before rerunning a rinse cycle to confirm the UE alert is gone.

Parts & Tools

• LG 5221DD1001F water inlet valve (restores proper fill during Test 5 when supply is good but the solenoid sticks)
• Klein Tools MM400 multimeter (checks for voltage at the dispenser, pumps, and diverter while you run service mode)

Resources