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Error code reference

Frigidaire Refrigerator Error Code Er CO

Communication error between Micom of Main PCB and Display Micom.

Frigidaire codesFrigidaire refrigerator codes

Communication error between Micom of Main PCB and Display Micom.

First step from the service manual

Check if the connection is loose on Display PWB CON101; measure voltage between pins 4 and 5 of CON101 for 0V or 5V.

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 Frigidaire refrigerator

The Er CO error code on a Frigidaire refrigerator indicates a communication failure between the main PCB's microcontroller (Micom) and the display board's microcontroller (Display Micom). These two control units exchange data continuously to coordinate temperature settings, user inputs, and operational status. When the signal pathway between them is interrupted or corrupted, the main PCB detects the loss of communication and triggers the Er CO fault code.

The communication link between the main PCB and the display board runs through connector CON101 on the display PWB. This connector carries a low-voltage data signal, typically operating at either 0V or 5V depending on the logic state. A loose, corroded, or damaged connection at CON101 is the most common physical cause of this error. Pins 4 and 5 of CON101 are the critical measurement points. If voltage at those pins reads outside the expected 0V or 5V range, that confirms a wiring or connector integrity problem rather than a component failure.

Beyond loose connectors, the fault can also originate from a failed display PWB, a damaged main PCB, or wiring harness damage between the two boards. Moisture, physical stress on wire routing, or component degradation on either board can disrupt the communication signal. Diagnosing the error requires methodically ruling out connector issues before concluding that a board replacement is necessary, since connector faults are far more common and less costly to resolve.

Source: manufacturer service documentation.

Common causes of Er CO

  1. 01

    Loose or disconnected CON101 connector

    Wiring / connection

    The connector at CON101 on the display PWB is the first place to inspect. A loose or partially seated connector will interrupt the 0V/5V communication signal between the two microcontrollers.

  2. 02

    Corroded or damaged connector pins

    Wiring / connection

    Corrosion or bent pins at CON101, particularly at pins 4 and 5, can prevent a stable voltage signal from passing through even if the connector appears seated. Inspect the pin contacts visually and clean if needed.

  3. 03

    Damaged wiring harness between main PCB and display board

    Part replacement

    The wiring harness connecting the two boards can suffer breaks, pinches, or chafing over time. A damaged harness will interrupt communication even if both boards are functioning correctly.

  4. 04

    Failed display PWB

    Part replacement

    If the connector and wiring check out but the voltage at CON101 pins 4 and 5 is still abnormal, the display board's microcontroller may have failed and will need to be replaced.

  5. 05

    Failed main PCB

    Part replacement

    If the display board is confirmed functional and all wiring is intact, the main PCB may be unable to generate or sustain the communication signal, requiring board replacement.

See the test procedure for each cause

Frequently asked questions about Er CO

What does Er CO mean on a Frigidaire refrigerator?
Er CO indicates a communication error between the main PCB's microcontroller and the display board's microcontroller. The two boards communicate over a low-voltage signal line, and when that connection is lost or corrupted, the refrigerator displays this fault code. The most common starting point for diagnosis is checking the CON101 connector on the display PWB and measuring voltage at pins 4 and 5.
Can I fix the Er CO error myself?
In many cases, yes. Start by unplugging the refrigerator and inspecting the CON101 connector on the display board to make sure it is firmly seated and the pins are not corroded or bent. If the connector looks secure, use a multimeter to check for 0V or 5V at pins 4 and 5 of CON101 after restoring power. If the readings are abnormal after confirming the connector is good, a wiring harness or board replacement may be needed, which is more involved but still possible for a skilled DIYer.
Will resetting the refrigerator clear the Er CO code?
A power reset by unplugging the refrigerator for a few minutes may temporarily clear the code, but it will return if the underlying communication problem is not resolved. If reseating the CON101 connector fixes the loose connection, the code should not return after a reset. A persistent Er CO code after a reset points to a wiring or board-level fault that requires further diagnosis.
Is it safe to keep using my refrigerator while it shows Er CO?
An Er CO error means the main control board and display panel are not communicating properly, which can affect the reliability of temperature control and user input functions. It is not advisable to rely on the refrigerator for extended periods while this fault is active, especially for storing medications or perishables that require precise temperature management. Address the fault as soon as possible to avoid potential food safety risks.
How much does it cost to repair the Er CO error on a Frigidaire refrigerator?
If the fix is simply reseating or cleaning the CON101 connector, there may be no parts cost at all. A replacement wiring harness typically runs in the range of $20 to $60 in parts. A new display board generally costs between $80 and $200, and a main PCB replacement can range from $100 to $300 or more depending on the model. Labor costs from a technician will add to these figures.

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