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Error code reference

LG Refrigerator Error Code PC Er

Communication error between MAIN MICOM and Panel MICOM (no response in 10 seconds after Main MICOM sends…

LG codesLG refrigerator codes

Communication error between MAIN MICOM and Panel MICOM (no response in 10 seconds after Main MICOM sends communication signal to Panel MICOM). Displayed as 'PC E' on RSG5B* models.

First step from the service manual

Check with oscilloscope or replace Main or Panel PCB as oscilloscope is needed for error check.

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

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What PC Er means on a LG refrigerator

The PC Er code on LG refrigerators indicates a communication failure between the Main MICOM (microcomputer) and the Panel MICOM. These two control boards exchange data signals continuously to coordinate display output, user input processing, and operational commands. When the Main MICOM sends a communication signal and receives no response from the Panel MICOM within 10 seconds, the unit triggers this error code. On RSG5B series models, the display renders this as 'PC E' due to character limitations on that display format.

The communication path between the two boards typically runs through a dedicated data line, and any interruption along that line can cause this fault. A loose or corroded connector between the boards is a common physical cause. Damage to the wiring harness, a failed Panel PCB, or a failed Main PCB can all produce the same symptom because any break in that signal chain prevents a successful handshake.

Diagnosing this code accurately requires an oscilloscope to inspect the actual communication signal being sent from the Main MICOM and verify whether it reaches the Panel MICOM. Without signal tracing equipment, the practical diagnostic approach is to inspect connectors and wiring first, then proceed to board replacement. Because the fault could originate on either board, identifying which board is faulty without an oscilloscope involves a process of elimination, starting with the less expensive panel board.

Source: manufacturer service documentation.

Common causes of PC Er

  1. 01

    Loose or disconnected wiring harness connector

    Wiring / connection

    The ribbon cable or connector linking the Main PCB to the Panel PCB can work loose over time due to vibration or handling. Visually inspect both ends of the harness and reseat any connectors that appear loose or show signs of corrosion.

  2. 02

    Failed Panel PCB

    Part replacement

    The Panel MICOM board itself may have failed, preventing it from receiving or responding to the Main MICOM's communication signal. This is a likely cause when wiring and connectors check out as intact.

  3. 03

    Failed Main PCB

    Part replacement

    If the Main MICOM is not correctly generating the communication signal in the first place, no response from the Panel board is possible. An oscilloscope check of the signal output from the Main PCB is needed to confirm this.

  4. 04

    Damaged wiring harness

    Part replacement

    A pinched, chafed, or broken wire in the harness between the two boards can interrupt the data line. Trace the full length of the harness and look for any visible damage, especially near sharp edges or areas with heat exposure.

See the test procedure for each cause

Frequently asked questions about PC Er

What does PC Er mean on a LG refrigerator?
PC Er indicates a communication error between the Main MICOM control board and the Panel MICOM control board. The Main MICOM sends a communication signal to the Panel MICOM and receives no response within 10 seconds, triggering this code. On RSG5B series models, the same fault appears as 'PC E' on the display. The error points to a breakdown somewhere in the signal path between the two boards.
Can I fix the PC Er error myself?
A homeowner or DIYer can start by unplugging the refrigerator and inspecting the wiring harness connectors between the Main PCB and Panel PCB for looseness or corrosion, then reseating them. Beyond that, accurate diagnosis requires an oscilloscope to trace the communication signal, which is a technician-level tool. If connectors are intact and the error persists, one or both control boards will need to be replaced, which most homeowners will want a technician to handle.
Is it safe to keep using my refrigerator while PC Er is displayed?
A PC Er code means the communication between the main control board and the display panel has broken down, which can affect how reliably the refrigerator responds to temperature commands and user inputs. It is not a high-voltage safety hazard, but continued operation with this fault may result in unreliable cooling or an inability to adjust settings correctly. Monitoring food temperatures closely is advisable, and prompt repair is recommended.
Will resetting the refrigerator clear the PC Er code?
Unplugging the refrigerator for a few minutes and restarting it may temporarily clear the code if the fault was caused by a transient software glitch or a brief signal interruption. However, if the underlying cause is a loose connector, damaged wiring, or a failed PCB, the PC Er code will return. A reset does not repair a hardware fault, so the code reappearing after a restart confirms a physical issue that needs further diagnosis.
How much does it cost to repair a PC Er error on an LG refrigerator?
Repair costs vary depending on which component is at fault. If only a connector needs reseating, labor charges may be the primary expense. A replacement Panel PCB typically runs in the range of $80 to $200 for the part, while a Main PCB can range from $150 to $350 or more, depending on the model. Adding a technician's diagnostic fee and labor, total repair costs commonly fall between $150 and $500 depending on which board requires replacement and your location.

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