LG Range F9 Error Code — What It Means
The F9 error code on an LG range means the upper oven is not heating properly. The oven failed to reach approximately 150°F within the first 5 minutes of preheat. This is a no-heat or slow-heat fault, not a keypad or control-panel button problem.
LG’s official guidance is to press CLEAR/OFF and retry the function, then power-cycle the breaker if the error returns. If the code persists after a reset, one or more components in the heating system has failed and needs diagnosis.
Common Causes
- Failed relay board or main control board The relay board or main control may no longer energize the heating element or igniter circuit, preventing the oven from heating even though all other components test good.
- Defective temperature sensor or thermistor The oven temperature sensor may be out of spec (normal room-temperature resistance is approximately 1080–1100 Ω on many LG models) or the sensor wiring may be damaged or loose.
- Blown thermal fuse The high-limit thermal fuse protects the oven from overheating and will open if a previous overheat event occurred, cutting power to the heating circuit.
- Weak or failed gas igniter On gas ranges, the igniter may glow orange but fail to draw enough current (typically around 3.0–3.6 A) to open the gas safety valve, so the oven never heats.
- Open bake heating element On electric ranges, the upper-oven bake element may have an internal break or visible blister, preventing current flow and heat production.
- Heat-damaged wiring or connectors Harness connectors near the element, sensor, or relay board may show melting, discoloration, or open pins that interrupt the heating circuit.
Step-by-Step Fix
- Press CLEAR/OFF on the range control panel, wait 60 seconds, then start a normal Bake cycle to see if the error clears.
- Power-cycle the breaker. Switch the circuit breaker off for 60 seconds, restore power, and retry Bake. If F9 returns immediately or within five minutes, proceed with component testing.
- Confirm the symptom. Set the upper oven to Bake at 350°F and listen and watch for the heating element to glow (electric) or the igniter to glow and the burner to light (gas). If nothing happens within five minutes, the oven is not heating.
- Inspect visible components. Unplug the range or shut off the breaker, remove the upper-oven racks, and look for a blistered bake element, burned wire insulation, or loose harness connectors behind the rear panel.
- Test the temperature sensor. Disconnect the sensor plug (usually a two-wire connector at the back wall of the oven cavity) and measure resistance across the sensor leads with an ohmmeter. Compare the reading to your model’s specification (many LG sensors read 1080–1100 Ω at room temperature). Replace the sensor if the reading is far out of range or open.
- Check the thermal fuse for continuity. Locate the thermal fuse on the back of the oven or on the control-board assembly, disconnect both leads, and test with an ohmmeter. Replace the fuse if it shows an open circuit.
- Verify element or igniter operation. On electric models, test the bake element for continuity (typically 15–50 Ω when cold). On gas models, measure igniter current draw during a Bake cycle (a weak igniter will glow but draw less than about 3.0 A). Replace the element or igniter if defective.
- Replace the relay or main control board if all field components (sensor, element or igniter, thermal fuse, wiring) test within specification but the oven still does not receive power to heat. Retest a full preheat cycle after board replacement.
Parts Often Needed
| Part | Notes |
|---|---|
| LG range relay board or main control board | Amazon | Match the board part number printed on your existing board. Some LG models use a separate relay board, others integrate relay circuits into the main EBR control. |
| LG oven temperature sensor / thermistor | Amazon | Two-wire probe that mounts through the rear oven wall. Verify the connector type and probe length for your model. |
| LG oven thermal fuse | Amazon | High-limit safety fuse, usually rated 250°F or higher. One-time device that must be replaced if blown. |
| LG range gas oven igniter (gas models) | Amazon | Round or flat ceramic hot-surface igniter. Confirm the mounting bracket and current rating match your burner valve. |
When to Call a Pro
Call a qualified appliance technician if you are uncomfortable working inside a 240 V electric range or around gas appliance components. High-voltage and gas connections require training and proper tools. A technician can perform live-circuit current measurements, verify control-board relay outputs with a multimeter, and safely replace internal wiring harnesses. If you have already replaced the sensor and thermal fuse but F9 persists, the fault is likely in the relay board or main control, and professional board-level diagnosis will save time and prevent unnecessary part swaps.