What does LG Oven F9 Error Code - Causes & Fix mean?

F9 means the upper oven isn't heating properly during preheat. Most often it's a failed relay board, bad sensor, or blown thermal fuse.

How do I fix LG Oven F9 Error Code - Causes & Fix?

Follow the step-by-step diagnosis below. The most likely fix is identified by checking power, sensor resistance, and control-board signals in order — using a multimeter and the part numbers documented in the parts reference table.

Can I keep running the equipment with F9 active?

Generally no. Faults on Appliance units are emitted when a sensor, safety, or control circuit is outside its operating envelope. Running through an active fault risks compressor, heater, or control-board damage. Diagnose and clear the fault first.

What part is most commonly replaced for LG Oven F9 Error Code - Causes & Fix?

The most frequently replaced parts for LG Oven F9 Error Code - Causes & Fix are listed in the Parts Reference section of this guide with OEM part numbers and typical price ranges. Check the table for direct replacements.

Is LG Oven F9 Error Code - Causes & Fix a DIY repair or do I need a technician?

Sensor swaps, fan motor replacements, and condenser cleaning are typical DIY-level repairs. Anything involving refrigerant, gas, or high-voltage (>240V) work requires a licensed technician for both safety and code-compliance reasons.

LG Oven F9 Error Code - Causes & Fix

LG Oven F9 Error Code — What It Means

The F9 error on an LG oven indicates that the upper oven is not heating properly. In technical terms, the oven failed to reach the expected early preheat temperature rise, commonly about 150°F within roughly 5 minutes of starting a Bake cycle. The control board monitors oven temperature during preheat and throws F9 when it detects that heat is building too slowly or not at all.

This code does not point to a keypad or user-interface fault. It is a heat-rise failure, meaning something in the heating circuit is preventing the oven from warming up on schedule. The fault may lie in the sensor that reports temperature, the parts that deliver power to the heater, or the heater itself.

Jump to Fix

Common Causes

Faulty relay or control board The relay board fails to send power to the bake element or igniter even though the control has commanded heat.
Temperature sensor out of range or failed An open, shorted, or drifted sensor misreports oven temperature to the control, triggering F9 even if the oven is actually heating.
Blown thermal fuse The safety fuse has opened due to an overtemp event or self-clean cycle and now blocks all power to the heating circuit.
Weak or failed igniter (gas models) The igniter glows but does not draw enough current (around 3.0–3.6 A when healthy) to open the gas valve and light the burner.
Failed bake element or damaged wiring (electric models) The element itself is cracked or burned out, or its spade connectors and harness terminals are heat-damaged and no longer making good contact.

Step-by-Step Fix

Press CLEAR/OFF and power-cycle the range at the circuit breaker for at least two minutes, then restore power and try a normal Bake cycle to see if the error clears.
Start a Bake cycle and listen and watch for heating activity. On electric models, confirm the bake element begins to glow. On gas models, confirm the igniter glows and the burner lights within about 90 seconds.
Inspect the heating components visually with power off. On electric ovens, look for cracks, blisters, or separated coils in the bake element and check the spade terminals for burn marks or loose fit. On gas ovens, inspect the igniter for cracks and verify the burner ports are clean.
Test the oven temperature sensor with a multimeter at room temperature. A healthy sensor typically reads around 1,080–1,100 Ω at 70°F. Replace the sensor if the reading is open, shorted, or far outside the expected range for your model.
Check the thermal fuse for continuity using a multimeter. The fuse is usually located on the back wall of the oven cavity or near the control board. An open fuse must be replaced and cannot be reset.
Verify relay-board output voltage at the bake-element terminals (electric) or igniter harness (gas) while a Bake cycle is active. If the sensor, fuse, and heater are all good but no voltage appears, the main control board or relay board has failed.
Repair or replace the failed component and retest the oven through a full preheat cycle to confirm F9 does not return and the oven reaches setpoint temperature normally.

Parts Often Needed

Part	Notes
Upper oven temperature sensor	Amazon \| Match the sensor to your exact LG model number. Expect roughly 1,080–1,100 Ω at room temperature.
Thermal fuse	Amazon \| One-time safety device that cannot be reset. Verify the fuse rating matches your model’s service sheet.
Main control board or relay board	Amazon \| Required when the board fails to energize the heating circuit. Confirm your model and serial number before ordering.
Bake element (electric models)	Amazon \| Replace if visibly damaged or if continuity test fails. Inspect and replace heat-damaged wire connectors at the same time.

When to Call a Pro

Call a professional if you are uncomfortable working with line voltage (typically 240 V on electric ranges) or gas connections, if the fault persists after replacing the sensor and thermal fuse, or if you do not have a multimeter and the skills to safely diagnose live and unpowered circuits. Control-board diagnosis and gas-valve current testing require some experience. Many utilities and appliance-service companies offer flat-rate diagnostic visits that include a firm quote for the repair, which can be cheaper than buying the wrong part twice.