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Error code reference

LG Range Error Code C-20

Oven sensor opened (over 2850 ohms) or oven sensor shorted (under 830 ohms).

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Oven sensor opened (over 2850 ohms) or oven sensor shorted (under 830 ohms).

First step from the service manual

Disconnect power. Open the back cover. Disconnect sensor harness from CN320 of Main PCB. Measure sensor resistance (approximately 1090 ohms at room temperature). If there are any problems, replace oven sensor.

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

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What C-20 means on a LG range

The C-20 error code on an LG range indicates a fault detected in the oven temperature sensor circuit. The control system continuously monitors the resistance of the oven sensor (also called an RTD or resistance temperature detector) to determine the oven cavity temperature. When the measured resistance falls outside the acceptable operating window, specifically above 2850 ohms or below 830 ohms, the main PCB flags the C-20 fault and halts normal oven operation to prevent overheating or inaccurate temperature control.

At room temperature, a properly functioning LG oven sensor should measure approximately 1090 ohms. A reading above 2850 ohms indicates an open circuit condition, meaning the sensor element has failed internally or the wiring harness has a break somewhere between the sensor and the main PCB connector CN320. A reading below 830 ohms points to a short circuit condition, where the sensor or its wiring has developed an unintended low-resistance path to ground or another conductor.

Common causes include a failed sensor element due to heat cycling stress over time, damaged wiring inside the oven cavity from high temperatures or physical contact with heating elements, and a corroded or loose connector at CN320 on the main PCB. In some cases the main PCB itself may misread the sensor signal, but this is far less common than sensor or wiring failure. Diagnosis begins with a simple resistance measurement at the harness connector after disconnecting power.

Source: manufacturer service documentation.

Common causes of C-20

  1. 01

    Failed oven temperature sensor

    Part replacement

    The sensor element itself has degraded or burned out, producing a resistance reading outside the 830 to 2850 ohm range. This is confirmed by measuring resistance at the harness after disconnecting power and finding a value well above or below the expected 1090 ohms at room temperature.

  2. 02

    Broken or open sensor wiring harness

    Part replacement

    The wires connecting the sensor to connector CN320 on the main PCB can crack or break due to repeated heat exposure inside the oven cavity. A visual inspection of the harness routing and a continuity check will reveal any open sections.

  3. 03

    Shorted sensor wiring

    Part replacement

    High heat can cause the insulation on the sensor wiring to melt or char, allowing two conductors to contact each other or a grounded metal surface. This produces an abnormally low resistance reading below 830 ohms.

  4. 04

    Loose or corroded connector at CN320

    Wiring / connection

    A poor connection at the CN320 harness connector on the main PCB can cause intermittent or falsely high resistance readings. Disconnecting, inspecting, and firmly reseating the connector may resolve the issue without part replacement.

  5. 05

    Faulty main PCB

    Part replacement

    If the sensor measures correctly at approximately 1090 ohms and the wiring harness checks out, the main PCB may be misinterpreting the sensor signal. Board replacement is the last resort after all other components have been ruled out.

See the test procedure for each cause

Frequently asked questions about C-20

What does C-20 mean on a LG range?
The C-20 code on an LG range means the control board has detected that the oven temperature sensor is operating outside its acceptable resistance range. A properly working sensor reads around 1090 ohms at room temperature. If resistance climbs above 2850 ohms, the sensor circuit is open. If it drops below 830 ohms, the circuit is shorted. Either condition prevents accurate temperature control and triggers this fault.
Can I fix the C-20 error myself?
A knowledgeable DIYer can diagnose and often fix C-20 by disconnecting power, opening the back cover, and measuring the sensor resistance at connector CN320 on the main PCB. If the reading is outside the 830 to 2850 ohm range, the sensor or its wiring needs replacement. Replacing an oven temperature sensor is a straightforward repair involving unplugging the harness and removing a few screws, but working inside the appliance does require comfort with basic electrical testing.
Is it safe to use my LG oven when C-20 is displayed?
No, you should not attempt to use the oven while C-20 is active. The error means the control board cannot accurately monitor oven temperature, which removes a critical safety safeguard against overheating. Disconnect power and have the sensor or wiring inspected before operating the range again.
Will resetting the power clear the C-20 error?
Resetting power by unplugging the range or switching off the circuit breaker may temporarily clear the display, but the code will return as soon as the oven attempts to operate if the underlying sensor or wiring fault is still present. A permanent fix requires diagnosing and correcting the out-of-range resistance condition in the sensor circuit.
How much does it cost to repair a C-20 error on an LG range?
If only the oven temperature sensor needs replacement, parts typically run in the range of $20 to $60 depending on the specific model, and a repair technician may charge $100 to $200 in total including labor. If the main PCB is at fault, parts alone can range from $150 to $300 or more, with labor added on top. Diagnosing the fault accurately before ordering parts will keep costs as low as possible.

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