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Error code reference

Kenmore Refrigerator Error Code Er CO

Communication error between MICOM of Main PCB and Display MICOM; caused by poor communication connection…

Kenmore codesKenmore refrigerator codes

Communication error between MICOM of Main PCB and Display MICOM; caused by poor communication connection, poor TR of transmitter/receiver Tx/Rx between display and main board.

First step from the service manual

Check loose connections, then check Red to White Red at CON101 for 12VDC.

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

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What Er CO means on a Kenmore refrigerator

Er CO indicates a communication failure between the main PCB's microcontroller (Main MICOM) and the display board's microcontroller (Display MICOM). The refrigerator's control system relies on a continuous data link between these two boards. When that link breaks down, whether due to a loose connector, a damaged wiring harness, or a failed transmitter/receiver (Tx/Rx) circuit on either board, the main PCB logs Er CO and surfaces it on the display. The diagnostic starting point is CON101, where the Red and White-Red wires should carry 12VDC; no voltage or intermittent voltage at this connector points directly to a wiring or power supply issue rather than a failed board.

For homeowners, this error means the two main electronic controllers inside your refrigerator have stopped talking to each other. Think of it as a dropped connection between the brain of the fridge and the control panel you interact with. The refrigerator may still run in some capacity, but without reliable communication between the boards, temperature regulation and user controls may not function correctly. The fix often starts simple, checking whether a wire connector has come loose, before moving on to testing voltage and potentially replacing a control board or wiring harness.

Source: manufacturer service documentation.

Common causes of Er CO

  1. 01

    Loose or disconnected wiring harness at CON101

    Wiring / connection

    The connector at CON101 links the main PCB to the display board. If this connector is partially seated or has worked loose from vibration, the 12VDC signal carried on the Red to White-Red wires drops out and triggers Er CO.

  2. 02

    Failed Tx/Rx communication circuit on main PCB or display board

    Part replacement

    The transmitter and receiver components on either the main board or the display board can fail, preventing the MICOM signals from passing between the two boards even when wiring connections are intact.

  3. 03

    Damaged or shorted wiring harness between display and main board

    Part replacement

    A wire in the harness running between the display board and main PCB can chafe, break, or short, interrupting the communication signal. This is common in areas where the harness bends around a door hinge or cabinet edge.

  4. 04

    No 12VDC output at CON101 due to main PCB power supply failure

    Part replacement

    If the main board's onboard power supply section has failed, it may not be producing the 12VDC required on the Red to White-Red lines at CON101, starving the display MICOM of power and causing the communication fault.

See the test procedure for each cause

Frequently asked questions about Er CO

What does Er CO mean on a Kenmore refrigerator?
Er CO stands for a communication error between the main control board's microcontroller (Main MICOM) and the display board's microcontroller (Display MICOM). The two boards send signals back and forth continuously, and when that link is interrupted by a loose connector, damaged wiring, or a failed transmitter/receiver circuit, the error appears. It is not a sensor failure or a compressor fault.
How do I fix Er CO on a Kenmore refrigerator?
Start by unplugging the refrigerator and inspecting the wiring harness connector at CON101 on the main PCB. Reseat any loose connectors and check the harness for visible damage. After reconnecting power, check for 12VDC on the Red to White-Red wires at CON101. If voltage is present and the error persists, the Tx/Rx communication circuit on the main board or display board has likely failed and one or both boards will need replacement. If there is no 12VDC at CON101, the main board itself may need to be replaced.
Is it safe to use my Kenmore refrigerator while it shows Er CO?
The refrigerator may continue cooling temporarily while Er CO is active, but the communication failure means the display controls and temperature management functions may not be operating reliably. You should not depend on the refrigerator to maintain safe food storage temperatures until the error is resolved. Check the actual temperature inside with a thermometer and plan to address the repair promptly.
How much does it cost to fix Er CO on a Kenmore refrigerator?
If the fix is simply reseating a loose connector at CON101, there is no parts cost. If the wiring harness is damaged, a replacement harness typically runs between $20 and $60. If the main PCB or display board needs replacement, parts range from $80 to $250 or more depending on the specific model, plus labor if you use a technician. Confirming 12VDC at CON101 before ordering parts helps avoid replacing the wrong component.
Will unplugging and replugging my Kenmore refrigerator clear the Er CO code?
A power reset may temporarily clear Er CO if the communication dropout was caused by a momentary glitch, but if the underlying issue is a loose connector, damaged harness, or failed board component, the code will return. Use the reset as a first step to confirm whether the error is persistent, then proceed with checking CON101 and the wiring harness.

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