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Error code reference

LG Hvac Error Code 2

PCB sees ODU or IDU thermistor(s) as open or shorted (varies by unit type

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PCB sees ODU or IDU thermistor(s) as open or shorted (varies by unit type: Inverter, 10/13 SEER, PTAC).

First step from the service manual

Ohm thermistor in water, measure water temperature. Pipe=2,800Ω at 38°C/100°F & 10,000Ω at 10°C/50°F (Inverter) or 5,000Ω at 25°C/77°F & 10,000Ω at 10°C/50°F (10/13 SEER). Air=5,600Ω at 38°C/100°F & 20,700Ω at 10°C/50°F. With perfect thermistor & plug connection, change PCB.

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

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What 2 means on a LG hvac

Error code 2 on LG HVAC systems indicates the main PCB (printed circuit board) has detected an open or shorted condition on one or more thermistors located in either the outdoor unit (ODU) or indoor unit (IDU). Thermistors are temperature-sensing resistors whose resistance changes predictably with temperature. When the PCB reads resistance values outside the expected range for current operating conditions, it flags an error rather than risk operating on faulty temperature data. The specific thermistors involved and their reference values differ depending on unit type: Inverter, 10/13 SEER, or PTAC.

For pipe (refrigerant line) thermistors on Inverter units, the expected resistance is approximately 2,800 ohms at 38 degrees C (100 degrees F) and 10,000 ohms at 10 degrees C (50 degrees F). On 10/13 SEER units, pipe thermistors should read approximately 5,000 ohms at 25 degrees C (77 degrees F) and 10,000 ohms at 10 degrees C (50 degrees F). Air thermistors across unit types should read approximately 5,600 ohms at 38 degrees C (100 degrees F) and 20,700 ohms at 10 degrees C (50 degrees F). Readings far outside these values indicate a failed or disconnected thermistor.

The proper diagnostic approach involves submerging the thermistor in water of a known temperature, measuring resistance with a multimeter, and comparing against the reference values above. If resistance checks out correctly and the connector plug is seated properly, the PCB itself is the likely fault. A shorted thermistor typically reads near zero ohms, while an open thermistor reads infinite (OL) resistance.

Source: manufacturer service documentation.

Common causes of 2

  1. 01

    Failed thermistor (open or shorted)

    Part replacement

    The thermistor itself has internally failed, producing a resistance reading of near zero (shorted) or infinite (open) when tested with a multimeter in water at a known temperature. This is the most frequent root cause of error code 2.

  2. 02

    Loose or corroded thermistor connector

    Wiring / connection

    The plug connecting the thermistor to the PCB may have worked loose or developed corrosion, creating an intermittent or open circuit. Inspecting and firmly reseating the connector at the board often resolves the error if the thermistor itself tests correctly.

  3. 03

    Damaged thermistor wiring

    Part replacement

    The wire harness between the thermistor and the PCB may be pinched, chafed, or broken, especially near routing edges or cabinet openings. Visually trace the wiring and check for continuity to rule this out.

  4. 04

    Thermistor exposed to moisture or refrigerant contamination

    Part replacement

    Condensation or refrigerant contact can degrade thermistor accuracy over time or cause an immediate short. If the sensor appears wet or discolored at the sensing tip, replacement is warranted.

  5. 05

    Faulty PCB

    Part replacement

    If all thermistors test within spec at their reference temperatures and all connectors are secure, the PCB's input circuit for thermistor monitoring may have failed. Board replacement is the corrective step after all other causes are ruled out.

See the test procedure for each cause

Frequently asked questions about 2

What does 2 mean on a LG hvac?
Error code 2 means the main control board has detected an open or shorted thermistor in the indoor or outdoor unit. Thermistors are temperature sensors, and the board monitors their resistance to track system temperatures. When resistance falls outside expected values for the current temperature, the unit flags the fault and may shut down. The specific thermistor involved depends on whether the unit is an Inverter, 10/13 SEER, or PTAC model.
Can I fix error code 2 on my LG HVAC myself?
A knowledgeable DIYer can check the thermistor connector plugs for secure seating and inspect wiring for visible damage. Accurately diagnosing the fault requires a multimeter and the ability to submerge the thermistor in water of a known temperature to compare resistance against the reference values for your unit type. If the thermistor or PCB needs replacement, the job involves handling electrical components and, depending on refrigerant line sensors, may require a licensed technician.
Is it safe to keep running my LG HVAC when error code 2 is displayed?
Operating the system while a thermistor fault is active is not recommended. The control board relies on accurate temperature data to prevent overheating, freezing, and compressor damage. Continued operation without valid sensor input increases the risk of additional component failures. The unit should be kept off until the fault is diagnosed and corrected.
How much does it cost to repair error code 2 on an LG HVAC unit?
If only a thermistor needs replacement, parts and labor typically fall in the range of $75 to $250 depending on the sensor location and unit model. If the PCB is the fault after thermistors test correctly, board replacement can range from $200 to $600 or more including labor. Costs vary by region and service provider.
Will resetting my LG HVAC clear error code 2?
A power reset may temporarily clear the fault display, but the error will return if the underlying thermistor or wiring problem still exists. The PCB continuously monitors thermistor resistance during operation, so any sensor reading outside the acceptable range will trigger the code again. A reset is only a lasting fix if the cause was a one-time transient event, such as a momentarily loose connector that has since been reseated.

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