LG Dishwasher PF: Power Interrupted During a Cycle

PF is not a component failure. It means the control board lost electrical power while a wash cycle was actively running and subsequently regained it. The board detected a clean power-on event with a cycle still registered as in-progress, meaning something interrupted the electrical supply mid-cycle.

PF Is a Symptom, Not a Disease

A single PF after a storm, breaker trip, or known power outage is completely normal. Clear it by pressing Start/Resume or by opening and closing the door. The dishwasher will either resume the interrupted cycle or allow you to start a new one.

PF becomes a diagnostic concern only when it repeats without any known power interruption. Recurring PF on an LG dishwasher with no breaker trips, no storms, and no other household power issues points to a problem at the dishwasher or its dedicated circuit.

Why PF Keeps Happening

Shared Circuit Under Load (40%)

LG dishwashers should run on a dedicated 15A or 20A circuit. In many homes, especially older construction, the dishwasher shares a circuit with the garbage disposal, kitchen lights, or countertop outlets. When multiple loads draw power simultaneously (disposal grinding while dishwasher heats, for example), the total current exceeds the breaker's rating. The breaker trips momentarily — sometimes so briefly you do not notice the lights flicker — but the dishwasher board detects the interruption.

Test: check your breaker panel. Identify the dishwasher breaker. If it is labeled "Kitchen" or shares a line with other outlets, that is your answer. The permanent fix is running a dedicated circuit — a licensed electrician's job.

Interim workaround: do not run the disposal while the dishwasher is mid-cycle. Avoid using high-draw countertop appliances (microwave, toaster oven, air fryer) on the same circuit.

Loose Electrical Connection (30%)

The junction box under the dishwasher is where house wiring connects to the machine's power cord or hardwired leads. Wire nuts loosen over time from thermal expansion cycles and vibration. A connection that is almost-but-not-quite making contact creates intermittent power dropouts.

Inspection (breaker off first):

1. Remove the junction box cover (under the dishwasher, near the kick plate area)
2. Check each wire nut connection — tug firmly on each wire. A loose wire pulls free
3. Any signs of heat damage (melted insulation, blackened wire nut, discolored copper) indicate a high-resistance connection that has been arcing
4. Remake connections with new wire nuts. Ensure 3-4 solid twists and tug-test each one

This is a fire hazard if left unaddressed. A high-resistance connection gets progressively hotter until it either melts the junction box or ignites nearby materials.

Board Power Supply Section (20%)

The main control board has a power supply section that converts 120VAC to the DC voltages the board logic needs. Electrolytic capacitors in this section age and lose capacitance over 7-10 years. A weakened capacitor cannot maintain voltage during the heater element's high-current phase — the board's own logic browns out momentarily, registers as a power loss, and posts PF.

Diagnosis clue: PF appears only during the wash or heated dry phase (when the heater is energized, drawing 10-15 amps). Never during the fill or rinse phases. This pattern strongly suggests internal board voltage sag, not external power issues.

Power Cord or Plug (10%)

If your LG dishwasher uses a plug rather than hardwired connection, check the outlet and plug for looseness. A plug that barely holds in the outlet can disconnect from vibration during the wash motor's run phase. Outlet contacts wear out — if the plug feels loose, replace the outlet.

What PF Does Not Mean

PF does not indicate any internal component failure (motor, pump, valve, heater). It solely reports a power supply interruption. Do not let anyone sell you a new wash motor or heater based on PF alone. If PF is the only code present, the machine's internal components are fine — the problem is getting consistent power to the machine.

Clearing PF

• Press Start/Resume once. The machine resumes or resets depending on how far the interrupted cycle had progressed
• If Start/Resume does not clear it, open the door, wait 5 seconds, close it, and press Start
• If PF returns within the same cycle, the power interruption source is still active

Parts and Cost

PF on GFCI-Protected Circuits

Some jurisdictions require dishwasher circuits to be GFCI-protected (2023 NEC onwards). GFCI breakers are more sensitive to nuisance tripping than standard breakers. Motor startup surges, heater element ground leakage at the edge of specification, and momentary moisture on wiring can trip a GFCI without tripping a standard breaker. If your dishwasher is on a GFCI circuit and PF recurs, the GFCI may be responding to a legitimate but minor leakage current that a standard breaker ignores. Have the heater element tested for ground fault — even a marginal reading (several megaohms to ground) can trigger a GFCI while being too small to trip a standard breaker.

PF During Storms vs. PF on Clear Days

PF during electrical storms is expected and harmless. PF on calm days with no grid issues is the diagnostic concern. Check with neighbors or your utility for any known voltage sag events in your area. Older neighborhoods with aluminum wiring or aging transformers experience micro-outages invisible to your lights but detectable by sensitive electronics like dishwasher control boards.

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LG dishwasher flashing PF repeatedly? We check the circuit, junction box, and board power supply to find the interruption source — not just reset the code. Book electrical diagnosis.