LG Cooktop Error Code F4

The F4 code on an LG cooktop indicates a fault with the right front top thermistor, which is the temperature sensor for that burner zone. The cooktop's control module monitors this sensor continuously and shuts down the right front zone when the resistance reading falls outside the expected range. At room temperature, the thermistor should measure between 500 and 550 K ohms at connector CN 04. Any reading significantly outside that range points to a sensor or wiring problem.

The right front burner zone will typically be disabled when F4 is active, which is the cooktop's built-in protective response. You should not attempt to bypass this lockout or continue using the affected zone until the fault is resolved. Other burner zones may still function normally, but the underlying sensor issue should be diagnosed and corrected before relying on the appliance for regular use.

Repair costs vary depending on which component has failed. A replacement thermistor is typically the least expensive part, while a control module replacement will cost considerably more. When factoring in professional labor, total repair costs can range from around $100 to $350 or more depending on your location and the specific parts needed. Getting a diagnostic visit from a qualified technician will give you a more precise estimate before committing to the repair.

A knowledgeable DIYer comfortable with a multimeter can perform the initial diagnosis by checking resistance at connector CN 04. If the thermistor reading is out of range, replacing the sensor is a feasible repair for someone familiar with appliance disassembly. However, if the wiring harness is damaged or the control module needs replacement, the repair becomes more complex and may warrant a qualified technician.

A power reset by unplugging the cooktop or cycling the circuit breaker may temporarily clear the F4 display, but the code will return if the thermistor or its wiring is genuinely out of specification. A reset alone does not correct a failed sensor or a damaged harness. Proper diagnosis at CN 04 is necessary to determine whether a component replacement is required for a lasting fix.