The LG refrigerator UC error code indicates a problem with the Ultra-Violet (UV) sanitizing module, often referred to as the UVnano feature in some models. This feature is designed to sanitize the water dispenser nozzle, helping to reduce bacteria and keep your water fresh. When this error appears, it means the system has detected a fault within the UV sanitization system.

Understanding the LG Refrigerator UC Error Code: UVnano Feature
LG refrigerators with UVnano technology utilize a UV LED within the dispenser to sanitize the nozzle. This process typically runs automatically for 10 minutes every hour. You can also manually activate it by pressing and holding the “Self Care” button for 3 seconds.
Key Features of UVnano Operation:
- Automatic Operation: The UV cleaning function automatically runs for 10 minutes every hour.
- Manual Activation: Press and hold the “Self Care” button for 3 seconds to manually activate the UV sanitization.
- Interruption: Pressing the Water button during operation will temporarily stop the UV cleaning cycle. It will resume automatically after one hour.
Causes of the UC Error Code
The most common cause of the LG refrigerator UC error code is a faulty UV LED module. However, the issue could also stem from a problem with the main control board (PCB) not supplying power to the UV module.
Troubleshooting Steps
Diagnosing the UC error requires some basic electrical testing. Here’s a breakdown of the troubleshooting process:
- Power Supply Check: The UV LED module requires 12V DC to operate. You’ll need a multimeter to perform this test.
- Testing the Main PCB:
- Locate the main PCB.
- Identify the pins connected to the UV LED module (in the provided example, pin 12 to pin 9).
- With the UV function active (either automatically or manually activated), measure the voltage between these pins.
- Expected Readings:
- 12V DC: This reading indicates the main PCB is supplying power correctly. If the UV LED is still not working, the UV module itself is likely defective.
- 5V DC (or no voltage): This reading suggests a problem with the main PCB, preventing it from sending the necessary power to the UV module. In this case, the main PCB may need replacement.
- Testing the UV Module: If the main PCB is providing 12V DC, but the UV LED is not illuminating, the UV module is faulty and needs to be replaced.
Important Notes:
Safety First: When working with electrical components, always exercise caution.
LG Refrigerator UC Error Code: Summary Table
Problem | Possible Cause(s) | Solution | Voltage Reading (Between Relevant PCB Pins) |
---|---|---|---|
UC Error Code, UV LED not illuminating | Faulty UV LED Module | Replace the UV Module | 12V DC (Main PCB is working) |
UC Error Code, UV LED not illuminating | Faulty Main PCB (not supplying power) | Replace the Main PCB | 5V DC or 0V (Main PCB is faulty) |
UVnano function not activating | Issue with “Self Care” button or control circuitry | Check button functionality; if faulty, consult a technician. Check wiring and connections to the control board. |

Mike Walker is an appliance repair technician with 15 years of experience dedicated to helping homeowners understand and fix their appliances. On this site, I break down complex error codes and offer easy-to-follow troubleshooting solutions.