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Error code reference

LG Hvac Error Code 48

PCB sees ODU coil outlet (liquid line) thermistor as open or shorted.

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PCB sees ODU coil outlet (liquid line) thermistor as open or shorted.

First step from the service manual

Must be 2,800Ω at 38°C/100°F & 10,000Ω at 10°C/50°F. Ohm thermistor in water; 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 48 means on a LG hvac

Error code 48 on an LG HVAC system indicates the outdoor unit (ODU) PCB has detected a fault condition with the coil outlet thermistor, also called the liquid line thermistor. This sensor monitors refrigerant temperature at the point where the liquid refrigerant exits the outdoor coil, which is critical data for the system's refrigerant flow and capacity calculations. The PCB triggers this code when the thermistor's resistance reading falls outside the expected range, indicating either an open circuit (broken or disconnected sensor) or a short circuit (wiring fault or failed sensor).

The thermistor must read approximately 10,000 ohms at 10°C (50°F) and approximately 2,800 ohms at 38°C (100°F). These reference points allow a technician to confirm whether the sensor itself has failed or whether a wiring/connector issue is causing the fault. To test accurately, the thermistor should be submerged in water at a known temperature and measured with an ohmmeter. A reading that deviates significantly from these values confirms thermistor failure.

If the thermistor resistance checks out correctly at both reference temperatures and the wiring harness and connector are secure with no visible damage or corrosion, the fault lies with the outdoor unit PCB itself. The PCB is misreading a good signal, which means the board requires replacement. Because this code can originate from either the sensor or the board, systematic component-by-component testing is essential before ordering any parts.

Source: manufacturer service documentation.

Common causes of 48

  1. 01

    Failed liquid line thermistor

    Part replacement

    The thermistor itself has failed internally, producing resistance values outside the expected range of 2,800 ohms at 38°C or 10,000 ohms at 10°C. Testing the sensor in water at a known temperature with an ohmmeter will confirm this.

  2. 02

    Loose or corroded thermistor connector

    Wiring / connection

    The plug connecting the thermistor to the PCB may be loose, corroded, or damaged, creating an intermittent or open circuit. Inspecting and reseating the connector is an early step before assuming the sensor or board has failed.

  3. 03

    Damaged wiring harness

    Part replacement

    The wiring between the thermistor and the PCB may be pinched, chafed, or broken, causing an open or short circuit condition. A visual inspection of the harness and a continuity check will identify this.

  4. 04

    Faulty outdoor unit PCB

    Part replacement

    If the thermistor tests within spec at both reference temperatures and the connector and wiring are intact, the outdoor PCB is misinterpreting a good signal. In this case the board itself requires replacement.

See the test procedure for each cause

Frequently asked questions about 48

What does 48 mean on a LG hvac?
Error code 48 means the outdoor unit PCB has detected that the coil outlet liquid line thermistor is reading as open or shorted. The PCB expects a resistance of about 10,000 ohms at 10°C (50°F) and 2,800 ohms at 38°C (100°F). When the sensor falls outside this range, the system faults out to prevent operating on bad data. The problem can be the thermistor itself, the wiring, the connector, or the PCB.
Can I fix error code 48 on my LG HVAC myself?
A knowledgeable DIYer can inspect the wiring and connector at the outdoor unit for visible damage, corrosion, or a loose plug, and reseating the connector sometimes clears the fault. However, accurately testing the thermistor requires an ohmmeter and the ability to measure the sensor at a known water temperature for comparison against the resistance spec. Replacing the PCB involves working with the outdoor unit's control board and is generally better left to a licensed technician.
Is error code 48 on a LG HVAC a safety risk?
Error code 48 itself does not represent an immediate safety hazard to people in the home. The system has shut itself down as a protective measure because it cannot reliably monitor the liquid line temperature. Leaving the system off until the fault is resolved is the correct approach, especially in extreme heat or cold conditions where operating a degraded system could lead to compressor damage.
How much does it cost to repair a LG HVAC error code 48?
Repair costs vary depending on which component has failed. A replacement thermistor is generally an inexpensive part, typically in the range of $15 to $60 for the sensor itself, plus labor. If the outdoor unit PCB is the cause, board replacement is significantly more expensive, with parts costs typically ranging from $150 to $500 or more depending on the model, plus the cost of a service call and labor.
Will resetting my LG HVAC clear error code 48?
A power reset may temporarily clear the code and allow the system to restart, but the fault will return if the underlying problem, whether a failed thermistor, damaged wiring, or a faulty PCB, has not been corrected. Repeatedly resetting without diagnosing the root cause can mask a problem that may eventually lead to compressor or system damage. A proper resistance test of the thermistor is needed to determine the correct repair.

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