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Error code reference

LG Refrigerator Error Code Ambient Air Sensor Error

External ambient air sensor system has errors.

LG codesLG refrigerator codes

External ambient air sensor system has errors.

First step from the service manual

Check voltage of MAIN PCB CN31#1 <-> #4: shall be between 4.5V~1.0V.

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

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  • Wiring diagram references and connector pinouts from the OEM service manual
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What Ambient Air Sensor Error means on a LG refrigerator

The Ambient Air Sensor Error on an LG refrigerator indicates a fault in the external ambient air temperature sensor circuit. This sensor monitors the temperature of the surrounding environment, which the main control board uses to make decisions about compressor operation, fan speeds, and overall cooling efficiency. When the sensor or its wiring circuit falls outside expected parameters, the main PCB registers this error and alerts the user.

The primary diagnostic checkpoint involves measuring voltage at connector CN31, pins 1 through 4, on the main PCB. Under normal operating conditions, this voltage should read between 1.0V and 4.5V. A reading outside this range indicates either a sensor that has shifted out of its calibrated resistance window, a wiring fault such as a short or open circuit, or a failed main PCB that is not supplying or reading voltage correctly. The sensor itself operates as a thermistor, meaning its resistance changes with temperature, and the control board interprets that resistance as a voltage signal within this defined window.

Common failure points include corrosion or damage at the sensor connector, a broken or pinched wire harness between the sensor and CN31, or a thermistor that has drifted out of specification due to age or moisture exposure. In some cases, the main PCB itself may be unable to properly process the sensor signal, though board failure is less common than sensor or wiring issues. Accurate diagnosis requires a multimeter to measure voltage at CN31 before replacing any components.

Source: manufacturer service documentation.

Common causes of Ambient Air Sensor Error

  1. 01

    Faulty Ambient Air Sensor (Thermistor)

    Part replacement

    The thermistor itself may have failed or drifted out of its calibrated resistance range, causing the voltage at CN31 pins 1 through 4 to fall outside the 1.0V to 4.5V window. Replacing the sensor is the most common fix when wiring checks out normal.

  2. 02

    Damaged or Disconnected Wiring Harness

    Wiring / connection

    A broken, pinched, or corroded wire between the ambient sensor and connector CN31 on the main PCB can interrupt the signal circuit. Visually inspect the harness for damage and check connector pins for corrosion or looseness.

  3. 03

    Loose or Corroded Connector at CN31

    Wiring / connection

    Poor contact at the CN31 connector on the main PCB can cause intermittent or absent voltage readings. Reseating the connector and cleaning corroded pins may resolve the error without part replacement.

  4. 04

    Moisture or Environmental Damage to Sensor

    Part replacement

    Exposure to condensation or humidity near the sensor location can degrade the thermistor or its connector over time, leading to inaccurate resistance values. Inspect the sensor housing and surrounding area for signs of moisture intrusion.

  5. 05

    Failed Main PCB

    Part replacement

    If voltage at CN31 pins 1 through 4 is absent or grossly incorrect even after confirming the sensor and wiring are intact, the main control board may have failed and is not properly supplying or reading the sensor circuit.

See the test procedure for each cause

Frequently asked questions about Ambient Air Sensor Error

What does Ambient Air Sensor Error mean on a LG refrigerator?
This error means the main control board has detected a problem with the external ambient air temperature sensor circuit. The sensor monitors room temperature to help regulate cooling performance. The board checks for a voltage signal between 1.0V and 4.5V at connector CN31, and when that signal is outside this range, the error is triggered. The root cause is typically a failed sensor, damaged wiring, or a loose connector.
Can I fix the Ambient Air Sensor Error myself on my LG refrigerator?
A knowledgeable DIYer can attempt this repair by first inspecting the wiring harness and connector at CN31 for obvious damage or looseness. Using a multimeter to check the voltage at CN31 pins 1 through 4 will help pinpoint whether the sensor, wiring, or control board is at fault. Replacing the ambient air thermistor is a relatively straightforward repair if the sensor is confirmed faulty. However, if the main PCB needs replacement, professional service is recommended.
Is it safe to keep using my LG refrigerator when this error is showing?
The refrigerator may continue to run with this error active, but its ability to optimize cooling based on room temperature will be compromised. This could lead to reduced efficiency or inconsistent temperatures over time. It is best to diagnose and resolve the fault promptly to avoid potential food safety concerns from improper cooling.
How much does it cost to repair the Ambient Air Sensor Error on a LG refrigerator?
If only the ambient air thermistor needs replacement, parts typically cost in the range of $15 to $50 depending on the specific model. If a service technician is required, labor costs can add $80 to $150 or more to the total. Main PCB replacement, if needed, is significantly more expensive, with parts alone ranging from $150 to $350 or higher.
Will resetting my LG refrigerator clear the Ambient Air Sensor Error?
A power reset may temporarily clear the error code, but if the underlying fault in the sensor circuit remains, the error will return once the control board runs its diagnostics again. Resetting is useful for confirming whether the fault is intermittent, but it is not a permanent solution. The voltage at CN31 should be measured and the sensor or wiring should be inspected to resolve the issue properly.

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