LG ranges and ovens show F-codes when the control sees a fault. The meanings below are from LG’s own Range Error Code List and owner’s documentation. Before anything else: two of the displays that bring us the most calls are not faults at all, so they come first.
H5 and 5b / Sb — not errors
H5 is the hot-surface indicator on glass cooktops — a burner is still above roughly 150°F. It clears as the surface cools. 5b / Sb means Sabbath mode is active: the oven holds a temperature and ignores most buttons, which reads like a frozen control. It is a press-and-hold to exit, shown in your model’s manual. Neither one needs a technician, and we will tell you so on the phone.
F1 / F2 — upper oven temperature sensor
The oven thermistor reads open or shorted. An oven that was running hot, cold, or slow to preheat before the code is the classic sensor failure, a modest repair. On double ovens, F4 / F5 is the same fault on the lower cavity.
F3 — a key is shorted
A control-panel button reads as held down. Moisture after cleaning or a stuck key; if it returns once dry, the panel needs service.
F6 / F9 — oven not heating
The oven did not reach temperature in the allowed time. On electric models the bake or broil element, a relay, or the sensor; on gas models the igniter or the gas valve. F9 is the one LG calls out in the owner’s manual as “oven not heating” — it is a symptom code, and the part behind it needs a meter.
F7 / F17 — convection fan
The convection fan did not run or did not report speed. A fan motor, its wiring or the relay. Baking still works on non-convection modes, so some owners live with this one; the oven will keep logging it.
F8 / F18 — meat probe
The temperature probe reads out of range: a damaged probe, a wet probe jack, or the jack itself. Unplugging the probe usually clears it; if it returns with no probe inserted, the jack or its wiring is the fault.
F10 / F20 — door lock
The upper (F10) or lower (F20) door lock did not reach its expected position. The lock motor, its switch, or a door not fully closed when self-clean engaged. A door that stays locked after self-clean is this assembly.
F11 / F38 — boards not communicating
The main control and the display or sub board have lost communication. A loose connector after a move or a power event, or a failed board.
F27 — cooling fan during self-clean
The cooling fan that protects the electronics during self-clean did not run. The oven aborts the clean to protect itself. Do not run self-clean again until this is fixed; the control board is what the fan is protecting.
F42 — supply voltage
The control is seeing incorrect voltage, usually a cord wired wrong at the terminal block on a new install, or a problem on one leg of the 240-volt circuit. A wiring correction rather than an oven repair, but a 240-volt one.
PF — power failure (not a fault)
Power was interrupted. Clear it and carry on. A PF that recurs with no outage points at a loose connection or cord worth checking.
Induction, grill and sous-vide codes
Induction cooktop-range models and models with built-in grill or sous-vide features carry an additional block of codes in the F33–F69 range for those modules. They follow the same pattern: sensor, communication, overheat. Note the exact code when you call.
Why we don’t recommend guessing parts
F9 can be an element, a relay, an igniter or a sensor. The code narrows the system; the meter identifies the part. We diagnose live, quote the actual repair, and the diagnostic fee is credited toward it. No code, just a cold oven? See oven not heating.
LG oven repair across the Denver Metro
FiXiFY repairs LG ranges and wall ovens across Denver, Aurora, Lakewood, Westminster and the metro — same-day in most areas, genuine OEM parts. See oven and range repair, the LG page, or the LG dishwasher codes guide.
BOOK ONLINECALL (303) 214-1240
FAQ
What does H5 mean on an LG range?
The cooktop surface is still hot, above roughly 150°F. It is an indicator, not an error, and clears as the glass cools.
My LG oven shows Sb and the buttons do not work. Is it broken?
No. Sb (5b) is Sabbath mode. The oven holds temperature and ignores most buttons on purpose. Exiting is a press-and-hold shown in your model’s manual.
What does F9 mean on an LG oven?
The oven did not reach temperature in time. LG lists it as oven not heating. The part behind it can be an element, a relay, an igniter or the sensor, which is why it needs a meter rather than a guess.
Is F27 serious?
It means the cooling fan did not run during self-clean, so the oven aborted to protect its electronics. Do not run self-clean again until the fan is repaired.
FiXiFY Appliance Repair — 7030 E 46th Ave Dr, Unit A, Denver, CO 80216 · (303) 214-1240 · support@fixifycolorado.com