LG Range F3 Error Code — Oven Temperature Sensor Fault

Your LG range displays F3 and the oven will not heat. This is a temperature sensor fault. The oven control board detects that the sensor circuit is open or shorted and locks out the oven for safety. Here is how to fix it.

Quick Reference

What F3 Means

The oven temperature sensor is a Resistance Temperature Detector (RTD). It sits on a metal bracket inside the oven cavity, usually at the back wall. It sends a resistance signal to the control board that tells the board the current oven temperature.

When this sensor fails outright (open circuit) or partially (shorted or drifted out of range), the board shows F3. The board will not turn on the bake or broil elements until the sensor circuit is restored.

Parts and Tools You Will Need

• LG oven temperature sensor (RTD) — check compatibility with your model number (check price on Amazon)
• Digital multimeter with resistance mode (on Amazon)
• Replacement wire harness for LG range (on Amazon)
• Oven control board — only if sensor replacement does not fix it (on Amazon)
• Phillips head screwdriver
• Nut driver or socket wrench (usually 1/4 inch)

Step-by-Step Fixes

Step 1: Reset the Oven

Sometimes F3 is a transient glitch from a power surge or a bumped control panel.

Press and hold the Clear/Off button for 3 seconds. If the F3 code disappears and the oven works normally, the error was temporary.

If the code stays on the display, open and close the oven door. Some LG models need the door switch to cycle before the board clears the error.

If F3 reappears the next time you try to use the oven, move to Step 2.

Step 2: Test the Oven Temperature Sensor

Safety: Turn off the breaker to the range at the electrical panel before going further. The oven is hardwired or plugged into a 240V outlet. 240V can kill you. Do not skip this step.

Step 1: Remove the oven racks so you can reach the back wall of the oven cavity.

Step 2: Locate the temperature sensor. It is a metal probe about 4 to 6 inches long mounted to the back wall with one or two screws. A wire harness connects it to the back of the unit.

Step 3: Remove the mounting screws holding the sensor bracket. Pull the sensor out slightly so you can unplug the wire connector. The connector is behind the oven at the control board area, or in some models accessible through a rear access panel.

Step 4: Set your multimeter to resistance mode. Connect one probe to each of the two sensor terminals.

Step 5: At room temperature (around 77°F / 25°C), a good LG oven RTD sensor reads approximately 1090 ohms. The specification is usually 1080 to 1100 ohms at room temperature.

Step 6: Test the sensor at different temperatures for a more complete check. For an accurate test, warm the sensor probe with your hand for 30 seconds. The resistance should decrease as the sensor warms. If it stays the same or jumps erratically, the sensor is bad.

Bad readings:

• Open circuit (OL on the meter) = failed sensor
• Short circuit (0 ohms) = failed sensor
• Reading under 500 ohms or over 2000 ohms at room temp = drifted out of spec

Step 3: Replace the Oven Temperature Sensor

If the sensor failed the resistance test, replacement is straightforward.

Step 1: Order the correct LG oven temperature sensor for your model. LG uses several different sensor mounting brackets and connector types. Check your model number before ordering.

Step 2: With the breaker still off, remove the old sensor mounting screws. Pull the wire harness through from behind.

Step 3: Feed the new sensor wire harness through the same hole. The connector is usually on the back of the unit behind the rear panel.

Step 4: Mount the new sensor probe in the same position with the same screws.

Step 5: Plug the connector into the control board. Some LG ranges need the connector pushed firmly until you feel or hear a click.

Step 6: Restore power. Press Clear/Off. Test the oven on Bake at 350°F.

Step 4: Check the Wiring Harness

If the sensor tested good (around 1090 ohms at room temp) but F3 still shows, the problem is in the wiring between the sensor and the control board.

Step 1: Unplug the sensor connector from the board.

Step 2: Set your multimeter to continuity mode (the speaker symbol). Place one probe on one pin of the sensor connector. Touch the other probe to the corresponding terminal on the sensor itself.

Step 3: Have a helper repeat this for the other wire while you watch the connector end.

Step 4: If either wire shows no continuity, or if the reading jumps when you wiggle the harness, the wire has a break or a bad connection.

Step 5: Replace the wire harness or repair the broken wire with a butt splice connector. Route the repair away from hot surfaces inside the oven.

Step 5: Replace the Control Board

If the sensor is good, the wiring is intact, and F3 persists, the control board has failed. This is the least common cause but it happens.

The control board is located behind the back panel of the range. Removing it requires disconnecting several wire harnesses. Take photos with your phone before pulling any connectors so you know where everything goes later.

Order a control board matched to your exact model number. Do not guess — LG uses different boards for gas vs electric, convection vs standard.

Preventing Future F3 Errors

• Do not use the self-clean cycle too often. The extreme heat (800°F+) stresses the sensor and the solder joints on the control board. Once per year is enough.
• Keep the oven sensor clean. Food spills on the sensor probe can cause it to read temperature incorrectly. Wipe the probe gently with a damp cloth when the oven is cool.
• Avoid slamming the oven door. Vibration over time can loosen the sensor mounting or damage the wire harness connections at the back.

When to Call a Professional

Call a technician if:

• You replaced the sensor, checked the wiring, and replaced the board — and F3 still shows
• You are not comfortable working with 240V appliances
• The range is under warranty

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