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Error code reference

LG Range Error Code C-31

PCB temperature sensor shorted or PCB temperature over (under 972 ohms) during 10 seconds.

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PCB temperature sensor shorted or PCB temperature over (under 972 ohms) during 10 seconds.

First step from the service manual

If this code was displayed, need to replace 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 range

The C-31 error code on an LG range indicates a fault with the PCB-mounted temperature sensor. Specifically, this code triggers when the sensor's resistance drops below 972 ohms and remains in that state for 10 or more consecutive seconds. This low-resistance condition tells the control board that the sensor is either shorted internally or that the PCB itself has reached an excessively high or abnormally low temperature threshold. The sensor is integrated into the main PCB assembly and monitors board-level temperature to protect the electronics from thermal damage.

The condition that triggers C-31 is distinct from oven cavity temperature sensor faults, which appear as different error codes on LG ranges. Here, the fault is localized to the circuit board itself. A shorted sensor means the sensor element has failed in a way that collapses its resistance to a value the board interprets as an out-of-range temperature reading. Whether caused by component degradation, heat damage to the board, or a manufacturing defect in the sensor circuit, the result is the same: the control board cannot trust its own thermal data and locks out normal operation.

Because the temperature sensor responsible for C-31 is embedded directly on the PCB rather than being a separately replaceable component wired to the board, there is no practical repair path involving individual sensor replacement. The entire PCB must be replaced to resolve this fault. Attempting to reset or cycle power may temporarily clear the display, but the code will return once the board re-evaluates sensor resistance during its startup or operational checks.

Source: manufacturer service documentation.

Common causes of C-31

  1. 01

    Shorted PCB temperature sensor

    Part replacement

    The most direct cause of C-31 is an internal short within the temperature sensor element on the PCB, causing resistance to fall below the 972-ohm threshold. This is confirmed when the fault persists across power cycles.

  2. 02

    Heat damage to the control board

    Part replacement

    Excessive heat exposure in the control board cavity can degrade sensor components and associated circuitry, causing sensor resistance to drop into the fault range. Visible burn marks or discoloration on the PCB may indicate this cause.

  3. 03

    Failed or degraded PCB components near sensor circuit

    Part replacement

    Capacitors, resistors, or traces adjacent to the sensor circuit on the PCB can fail over time and alter the effective resistance the board reads from the sensor. This type of failure typically worsens over time rather than appearing intermittently.

  4. 04

    Manufacturing defect in the sensor circuit

    Part replacement

    In some cases, the sensor or its associated circuitry may have a latent defect that manifests after a period of normal operation. This is more common in units that develop C-31 early in their service life.

See the test procedure for each cause

Frequently asked questions about C-31

What does C-31 mean on a LG range?
C-31 indicates that the temperature sensor mounted on the main PCB has either shorted or is reading a resistance below 972 ohms. The fault must persist for at least 10 seconds before the code is displayed. This is a board-level fault rather than a fault with the oven's cavity temperature probe. Resolving it requires replacing the main PCB.
Can I fix a C-31 error myself without replacing the board?
There is no field-serviceable repair for C-31 short of replacing the PCB, because the temperature sensor is integrated directly onto the board rather than connected as a separate component. Cleaning connections or resetting the unit will not correct a confirmed sensor short. If you are comfortable sourcing and installing a compatible replacement PCB, the repair is technically straightforward for an experienced DIYer.
Is it safe to use my LG range while it is showing a C-31 error?
You should not continue using the range while C-31 is active. The error indicates the control board cannot reliably monitor its own thermal state, which means protective shutoff functions tied to board temperature may not operate correctly. Discontinue use until the PCB has been replaced.
How much does it cost to fix a C-31 error on an LG range?
The primary cost is the replacement PCB, which typically runs between $150 and $350 depending on the specific model. If you hire a technician to perform the repair, expect total costs including labor to fall in the range of $250 to $500 or more. Getting a repair quote from an authorized service provider before committing is advisable, particularly for older units where part cost may approach replacement cost.
Will resetting my LG range clear the C-31 error code?
Cycling power or performing a reset may temporarily clear the C-31 code from the display, but the error will return once the control board re-checks the sensor resistance and again detects a reading below 972 ohms. A reset does not address the underlying hardware fault. Permanent resolution requires PCB replacement.

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