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Error code reference

LG Oven Error Code C-31

The PCB temp sensor is shorted when the oven is operating.

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The PCB temp sensor is shorted when the oven is operating.

First step from the service manual

Disconnect power. Open back cover. Replace the Main PCB.

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

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What C-31 means on a LG oven

The C-31 error code on an LG oven indicates that the PCB (printed circuit board) temperature sensor has detected a short circuit condition while the oven is in operation. The main PCB on many LG ovens includes an onboard thermistor or temperature sensing circuit that monitors the board's own operating temperature. When this internal sensor reports a shorted signal, the control board interprets the reading as invalid and triggers the C-31 fault to protect the appliance from operating under unknown thermal conditions.

A shorted PCB temperature sensor typically means the sensor's resistance has dropped to near zero ohms, causing the control circuit to read an out-of-range value. This differs from an open-circuit fault, where resistance would spike to infinity. The short can occur within the sensor component itself, in the traces on the board connecting the sensor to the control circuit, or in associated wiring. Heat damage, moisture intrusion, or a manufacturing defect in the board can all produce this condition.

Because the temperature sensor involved is integrated into or directly mounted on the main PCB rather than being a standalone probe with a separate wiring harness, the diagnostic path is straightforward. Disconnecting power, removing the back cover to access the main board, and replacing the PCB is the prescribed corrective action. There is no external sensor harness to test or swap independently in this case, making PCB replacement the direct resolution.

Source: manufacturer service documentation.

Common causes of C-31

  1. 01

    Failed onboard PCB temperature sensor

    Part replacement

    The thermistor or temperature sensing component soldered directly onto the main PCB has internally shorted. This is the most direct cause of C-31 and requires replacing the main PCB.

  2. 02

    Heat damage to the main PCB

    Part replacement

    Excessive heat inside the control cavity can damage PCB traces and components, causing a short in the temperature sensing circuit. Inspect the board for discoloration, burnt areas, or visibly damaged components before ordering a replacement.

  3. 03

    Moisture or contamination on the PCB

    Wiring / connection

    Moisture or grease contamination reaching the control board can create a conductive path across the sensor circuit, simulating a short. Check the board surface for corrosion or residue buildup.

  4. 04

    Manufacturing defect in the PCB

    Part replacement

    In some cases, a latent defect in the board's sensor circuit can cause premature failure and a shorted reading. If the oven is relatively new and shows no signs of heat or moisture damage, a defective board is a likely cause.

See the test procedure for each cause

Frequently asked questions about C-31

What does C-31 mean on a LG oven?
C-31 on an LG oven means the temperature sensor located on the main PCB (control board) has shorted while the oven is running. This is an internal board-level sensor, not the oven cavity temperature probe. The fault prevents the oven from operating safely until the condition is resolved, and the fix requires replacing the main PCB.
Can I fix the C-31 error myself?
The prescribed repair is to disconnect power, remove the back cover, and replace the main PCB. A technician comfortable with appliance disassembly and component replacement can complete this repair. However, working near high-voltage components carries risk, so if you are unsure, hiring a qualified technician is the safer choice.
Is it safe to use my LG oven while it shows C-31?
No, you should not use the oven while C-31 is active. The error indicates the control board's temperature monitoring circuit has shorted, meaning the board cannot reliably manage its own thermal condition. Continued operation risks further damage to the control board or other oven components.
Will resetting the oven clear the C-31 error?
A power reset may temporarily clear the fault code from the display, but C-31 will return once the oven is operated again because the underlying short in the PCB temperature sensor circuit has not been repaired. The only lasting fix is replacing the main PCB.
How much does it cost to repair a C-31 error on an LG oven?
The primary cost is the main PCB replacement part, which typically ranges from $150 to $350 depending on the specific LG model. If you hire a technician, labor costs can add another $100 to $200 to the total. Comparing the repair cost to the age and value of the oven is worth considering before proceeding.

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