Step-by-Step DIY Fix Guide
- SAFETY: Turn off the oven and disconnect power at the circuit breaker.
- Reset by restoring power after 60 seconds and testing a short bake cycle in the lower oven.
- If F4 returns, locate the lower oven temperature sensor — mounted to the back wall of the lower oven cavity.
- Unscrew the sensor and reconnect the harness connector firmly.
- Test the sensor resistance with a multimeter — at 70°F it should read approximately 1080–1090 ohms. Replace if open circuit.
If the warning comes back after restart
- If the warning returns immediately after a clean restart, the sensor or wiring path becomes more likely than a one-time glitch.
- F4 persists after reconnecting the sensor harness and multimeter confirms open circuit but replacement does not resolve it
What This Error Means
Error F4 on your LG oven means: The lower oven cavity temperature sensor (thermistor) is reading an open circuit on double-oven models. The lower oven cannot monitor temperature and the lower cavity is disabled. The range's self-diagnostic system has detected this condition.
The most frequent cause is lower oven thermistor has failed — open circuit. Work through the causes and fix steps below in order — many LG oven errors are resolved without a service call.
Many cases of F4 can be resolved by the homeowner. The steps below cover the full DIY checks — if they do not resolve the error, a technician is needed.
Oven temperature sensor faults are among the most common LG oven errors. The sensor is a simple probe on the back wall of the oven cavity — reconnecting a loose harness connector resolves around half of all sensor fault codes. Sensor replacement is a 15-minute DIY repair when the connector check does not resolve it.
Most Likely Cause by Symptom
The LG oven may stop, pause, or refuse to complete the cycle normally.
Likely cause: Lower oven thermistor has failed — open circuit
Check first: SAFETY: Turn off the oven and disconnect power at the circuit breaker.
The warning may return immediately because the appliance is detecting an internal fault.
Likely cause: Wiring harness connector to the lower oven sensor has come loose
Check first: Reset by restoring power after 60 seconds and testing a short bake cycle in the lower oven.
Common Causes
- Lower oven thermistor has failed — open circuit
- Wiring harness connector to the lower oven sensor has come loose
- Lower oven thermistor damaged by contact with bakeware
What Not to Do
- Do not use the lower oven with F4 active — without temperature monitoring, the cavity may overheat
Model and Display Variation Notes
Model-family notes
- LG oven display wording and code formats can vary by series.
- If your model behaves differently, check the owner manual before trying any deeper maintenance step.
Display and panel differences
- Panel wording can vary by series, so confirm the exact code pattern before buying parts.
Parts, Tools and Service Options
Service option
LG service visit if the warning returns after the basic checks are complete.
Manual and model check
Check your exact model and manual before ordering any LG oven parts.
Common parts
- Lower oven temperature sensor/thermistor if sensor has failed ($15–$40)
This section stays service-first because the page points more strongly toward support or professional repair than a routine parts purchase.
When Not to Keep Troubleshooting
F4 persists after reconnecting the sensor harness and multimeter confirms open circuit but replacement does not resolve it
How to Prevent It Recurring
- Use correctly sized bakeware in the lower cavity — pans that extend to the back wall can contact and damage the sensor probe
Related Error Codes
F1
The upper oven temperature sensor (thermistor) is reading an open circuit — its resistance is outside the valid range, meaning the oven cannot monitor temperature in the upper cavity.
F5
The lower oven temperature sensor is reading a shorted condition or the lower oven cavity has exceeded a safe operating temperature.
F11
The oven's display/control panel and the main control board have lost communication. The two boards cannot exchange data, so the oven cannot accept commands or display status correctly.
Extra notes
- This page is based on LG support material and stays conservative where model-specific guidance may vary.
- The goal is to help you identify safe first checks before you move into parts, service, or model-specific manual lookup.
Source and model notes
Last reviewed: 2026-04-08
Based on: Based on LG support material and edited into consumer-safe guidance for the exact code family on this page.
Model coverage note: LG oven code meanings can vary by series, control panel, and model family, so use this page as a safe starting point rather than a replacement for the model-specific manual.
Important: FixThisError is an independent guide, not the manufacturer. Use your model-specific manual when the panel wording or behavior differs.
Always disconnect power before inspecting appliances. If unsure, contact a licensed appliance technician.