mypros+
Error code reference

LG Oven Error Code F-9

Upper oven does not heat

LG codesLG oven codes

Upper oven does not heat — oven temperature does not exceed 150°F/66°C in less than 5 minutes.

First step from the service manual

Check thermostat open/short between DLB Relay L2 connections; check electric wiring and heater resistance.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

MyPros+ Max

Get the full diagnostic procedure for F-9.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What F-9 means on a LG oven

The F-9 error code on an LG oven indicates a heating failure in the upper oven cavity. Specifically, the control board has detected that the oven temperature did not rise above 150°F (66°C) within the first 5 minutes of a heating cycle. This threshold check is performed early in the preheat phase to confirm that the heating elements are producing heat. When the temperature sensor does not register adequate rise within that window, the board interprets this as a failure in the heating circuit and triggers the F-9 fault.

The diagnostic focus for this code centers on the DLB (Double Line Break) relay and the L2 power leg it controls. The DLB relay is responsible for switching the 240V circuit that powers the bake and broil elements. A thermostat or relay that is open or shorted across the L2 connections will interrupt current delivery to the heating element, preventing any temperature rise. Technicians should check for continuity and proper switching behavior at the DLB relay, and also inspect the associated wiring harness for damage, loose terminals, or burned connectors.

If the relay and wiring check out, the upper oven heating element itself should be tested for resistance. A failed element will typically show an open circuit (infinite resistance) when measured with a multimeter. In some cases, the oven temperature sensor (RTD probe) may also be at fault, reporting an inaccurate temperature reading that prevents the control board from seeing adequate heat rise even if some heating is occurring. Verifying the sensor's resistance value against its expected curve at room temperature is a useful secondary check.

Source: manufacturer service documentation.

Common causes of F-9

  1. 01

    Failed upper oven heating element

    Part replacement

    The bake or broil element in the upper oven cavity may have burned out and gone open circuit. Inspect the element visually for breaks or burn marks and confirm with a multimeter reading of infinite resistance.

  2. 02

    Faulty or stuck DLB relay

    Part replacement

    The Double Line Break relay controls the L2 power leg to the heating element. If the relay contacts are open, shorted, or stuck, the element will not receive the full 240V it needs to heat. Check for proper switching and continuity across the relay contacts.

  3. 03

    Open or damaged wiring in the heating circuit

    Wiring / connection

    Wiring between the DLB relay and the heating element can develop open connections, burned terminals, or loose connectors. Inspect the full wiring harness on the L2 circuit for signs of heat damage or disconnection.

  4. 04

    Defective oven temperature sensor

    Part replacement

    The RTD temperature probe may be reading incorrectly and reporting a temperature that appears too low to the control board, even if some heat is present. Test the sensor's resistance at room temperature and compare it to the expected value for the sensor type.

  5. 05

    Control board failure

    Part replacement

    If the relay, wiring, element, and sensor all test correctly, the control board itself may not be sending the proper signal to activate the DLB relay. This is a less common cause and should be diagnosed after all other components have been ruled out.

See the test procedure for each cause

Frequently asked questions about F-9

What does F-9 mean on a LG oven?
The F-9 code means the upper oven failed to reach 150°F (66°C) within 5 minutes of starting a heating cycle. The control board monitors temperature rise during preheat, and when it does not detect adequate heat in that window, it faults with F-9. This points to a problem in the heating circuit, which includes the heating element, the DLB relay controlling the L2 power leg, and the wiring between them.
Can I fix the F-9 error code myself?
Some steps, such as inspecting visible wiring connections and testing component resistance with a multimeter, are within reach for a knowledgeable DIYer comfortable working on appliances. However, the upper oven circuit operates on 240V, which is dangerous if not handled carefully. Replacing a heating element is a moderately straightforward repair, but testing and replacing a DLB relay or control board is best handled by a qualified technician if you are not experienced with high-voltage appliance circuits.
Is it safe to use my LG oven when the F-9 code is displayed?
No. When F-9 is active, the upper oven is not heating properly, which means food will not cook safely or evenly. More importantly, an underlying wiring or relay fault can present a fire or electrical hazard. The oven should not be used until the cause of the error has been identified and repaired.
Will resetting my LG oven clear the F-9 error code?
A power reset by unplugging the oven or turning off its circuit breaker for a few minutes may temporarily clear the code, but it will return as soon as a heating cycle is attempted again if the underlying fault is not repaired. The F-9 code is triggered by a real hardware failure in the heating circuit, and no amount of resetting will fix a failed element, relay, or wiring problem.
How much does it cost to repair an LG oven F-9 error?
Repair costs vary depending on the failed component. A replacement upper oven heating element typically costs between $30 and $100 for the part. A DLB relay or control board replacement can range from $80 to $250 or more depending on the part. Adding professional labor, total repair costs commonly fall between $150 and $400, though this varies by region and the specific parts required.

Related LG oven codes

All LG oven codes
View all 25 LG oven codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass