What F4, F5 (Lower Oven Thermistor Error) Means
F4 and F5 both indicate a Lower Oven Thermistor Error on double-oven range models, per LG's range Help Library article - the lower-cavity counterpart to F1/F2 on the upper oven.
Common Causes of F4, F5 (Lower Oven Thermistor Error)
- Lower oven thermistor has failed or lost contact
- Wiring connector to the thermistor has come loose
🔧 One Safe Check You Can Try
Press the CLEAR/OFF key and try the original function again; if the code reappears, cycle the circuit breaker for 30 seconds before trying once more.
⚠ Why You Shouldn't Go Further Than That
- If a breaker cycle doesn't clear a repeat F4 or F5, the lower oven's thermistor needs a technician to access and replace, the same as F1/F2 on the upper cavity.
- Don't rely on the lower oven for precise temperature cooking until this is resolved, since the fault means the control board can't confirm the cavity is actually at the set temperature.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.