mypros+
Error code reference

LG Cooktop Error Code F1

Front left top thermistor fault.

LG codesLG cooktop codes

Front left top thermistor fault.

First step from the service manual

Check CN 03 (Left Module); thermistor should read 500~550 K ohms at room temperature.

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 F1.

  • 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 F1 means on a LG cooktop

The F1 error code on an LG cooktop indicates a fault in the front left top thermistor circuit. The thermistor is a temperature-sensing resistor embedded near the front left cooking zone that continuously monitors surface or element temperature and feeds that data to the control module. When the control board detects that the resistance reading from this thermistor falls outside the expected operating range, it triggers the F1 fault and typically disables the affected zone as a safety measure.

The first diagnostic step is to inspect connector CN 03, which serves the left module. At room temperature, a properly functioning thermistor should measure between 500 and 550 K ohms. Readings significantly above or below this range indicate a failed thermistor, while a reading of zero ohms or open circuit (infinite resistance) can point to a wiring fault or a completely failed sensor. The connector itself should also be inspected for corrosion, loose pins, or heat damage, as a poor connection at CN 03 can mimic a thermistor failure.

Common causes include physical damage to the thermistor from overheating, a broken or shorted wire in the harness between CN 03 and the sensor, moisture intrusion into the connector, or a failed thermistor component. In rarer cases, the control board itself may be misreading a valid signal, though this is typically ruled out only after the thermistor and wiring are confirmed to be within specification.

Source: manufacturer service documentation.

Common causes of F1

  1. 01

    Failed thermistor

    Part replacement

    The thermistor itself has failed and is no longer reading within the 500 to 550 K ohm range expected at room temperature. This is the most likely cause and can be confirmed with a multimeter at connector CN 03.

  2. 02

    Loose or corroded CN 03 connector

    Wiring / connection

    The connector on the left module can develop corrosion or a loose pin contact, causing intermittent or incorrect resistance readings. Inspect the connector for discoloration, pitting, or pins that are not fully seated.

  3. 03

    Damaged thermistor wiring harness

    Part replacement

    The wire harness running between the thermistor and CN 03 may have a break, short, or heat-damaged section. Visually trace the harness for melted insulation, pinched wires, or visible breaks.

  4. 04

    Thermistor overheated from spill or excessive heat

    Part replacement

    Liquid spills or sustained extremely high temperatures can permanently alter the thermistor's resistance characteristics. This type of damage usually results in a reading well outside the 500 to 550 K ohm specification.

  5. 05

    Faulty left control module or main board

    Part replacement

    If the thermistor and all wiring measure within specification but the F1 code persists, the left control module connected at CN 03 may be misinterpreting the signal. This is the least common cause and should be diagnosed only after all other components are verified.

See the test procedure for each cause

Frequently asked questions about F1

What does F1 mean on a LG cooktop?
The F1 code on an LG cooktop indicates a fault with the front left top thermistor. The thermistor is a resistance-based temperature sensor, and the control board has detected that the reading from this sensor is outside the normal range of 500 to 550 K ohms at room temperature. The cooktop typically disables the front left zone until the fault is resolved.
Can I fix the F1 error on my LG cooktop myself?
A knowledgeable DIYer comfortable with electrical testing can begin by checking connector CN 03 on the left module for loose or corroded pins and measuring the thermistor resistance with a multimeter. If the thermistor reads outside 500 to 550 K ohms, replacing the sensor is the likely fix. However, working inside a cooktop involves electrical components that can pose a shock hazard, so unplugging the unit before any inspection is essential, and complex repairs are best handled by a qualified technician.
Is it safe to keep using my LG cooktop with an F1 error?
It is not recommended to continue using the affected cooking zone while the F1 error is active. The error means the cooktop cannot reliably monitor the temperature of the front left burner, which removes a key safety protection. Other zones may still function normally, but the front left zone should be considered out of service until the fault is diagnosed and repaired.
Will resetting my LG cooktop clear the F1 error?
A power reset by unplugging the cooktop or switching off the circuit breaker for a few minutes may temporarily clear the F1 code, but if the underlying thermistor or wiring fault is still present, the error will return once the unit powers back on. A permanent fix requires testing and, if necessary, replacing the thermistor or repairing the wiring at CN 03.
How much does it cost to repair an F1 error on an LG cooktop?
Repair costs vary depending on the root cause. Thermistor replacement parts typically range from around 20 to 80 dollars, while a control module can be considerably more expensive. Adding a technician's labor, total repair costs generally fall somewhere between 100 and 350 dollars depending on your location and the specific parts required.

Related LG cooktop codes

All LG cooktop codes
View all 16 LG cooktop codes

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

Get Started

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