LG · Oven
LG Oven F4 Error Code
Oven temperature sensor open circuit
What this error means
F4 is the open-circuit counterpart to F3—the temperature sensor or its wiring reads infinite resistance, so the control cannot detect oven temperature.
How F4 is detected
LG oven models lock the door or lid before energizing fill, heat, or high-speed spin. F4 means the latch switch never sent a "locked" signal to the main control, or the lock motor did not complete its travel. On LG LRG4115ST, LG LREL6325F, and similar variants, clothing caught in the gasket, a misaligned strike, or a failed latch assembly are the most common mechanical causes—not the board itself.
Inspect the door gasket perimeter and strike alignment before replacing the latch. Sensor connector CN31 loose at main PCB is reported frequently on this code. After correcting mechanical issues, power off and reseat cn31 at the main board. If the latch clicks but F4 persists, the door lock switch or wiring harness to the control board likely needs testing with a multimeter.
Do not force the door open during an active cycle; wait for the lock to release when the board de-energizes the lock motor—usually two to three minutes after canceling power on most LG units.
Common causes
- Sensor connector CN31 loose at main PCB
- Broken sensor wire inside the oven cavity insulation
- Failed RTD element internally open
- Previous repair left sensor unplugged
Step-by-step fixes
- 1Power off and reseat CN31 at the main board
- 2Measure sensor at the probe: open reading confirms replacement needed
- 3Compare with LG spec chart printed on service manual for your model year
- 4Retry preheat after reseat if ohms were borderline
When to call a technician
Open sensor with intact wiring requires probe replacement—access from inside the oven rear wall.
Affected models
- LG LRG4115ST
- LG LREL6325F
- LG LDG4315ST
Prevention & maintenance
- Wipe the door gasket weekly and avoid overloading items against the seal—F4 often starts as a slow leak or latch misalignment.
- Record when F4 appears in the cycle and whether it clears after a 60-second power reset on your LG oven—that detail speeds diagnosis if you call service.
- Keep the model and serial number from the rating plate when ordering parts for F4; LG uses multiple revisions with different harness lengths and board firmware.
- Photograph wiring connector orientation before disconnecting any component while troubleshooting F4; reversed plugs on pumps and valves cause immediate repeat faults.