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Error code reference

Electrolux Oven Error Code F21

Communication problem between the User Interface Board and the Appliance Control Board

Electrolux codesElectrolux oven codes

Communication problem between the User Interface Board and the Appliance Control Board: the User Interface Board is no longer able to detect communication from the Appliance Control Board.

First step from the service manual

Check the communication harness from connector P20 (pins 1,2,7,9,11) on the Appliance Control Board to connector J2 on the User Interface Board.

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

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What F21 means on a Electrolux oven

The F21 error code on an Electrolux oven indicates a communication failure between two core control components: the User Interface Board (UIB) and the Appliance Control Board (ACB). Specifically, the UIB has lost the ability to detect incoming communication signals from the ACB. These two boards work in tandem to coordinate user inputs with oven functions, and the data link between them runs through a dedicated communication harness. When that link is broken or degraded, the UIB can no longer receive instructions or status signals from the ACB, triggering the F21 fault.

The communication harness connecting these two boards is the first and most critical area to inspect. The harness runs from connector P20 on the Appliance Control Board, using pins 1, 2, 7, 9, and 11, to connector J2 on the User Interface Board. Any break, loose seating, corrosion, or damaged wire along this specific path can interrupt the data signal and produce this fault. Because multiple pins are involved, a single compromised pin is sufficient to cause the error.

Beyond the harness itself, the fault can also originate from a failed Appliance Control Board that is no longer transmitting signals, or a User Interface Board that cannot receive them even when signals are present. Heat cycling, moisture exposure, and connector fatigue are common contributors to harness and board failures in oven environments. Diagnosing the root cause requires methodically checking the harness continuity and connector integrity before condemning either board.

Source: manufacturer service documentation.

Common causes of F21

  1. 01

    Loose or disconnected communication harness connector

    Wiring / connection

    The connector at P20 on the Appliance Control Board or J2 on the User Interface Board may have worked loose over time due to vibration or heat cycling. Reseating both connectors firmly is the first physical check to perform.

  2. 02

    Damaged or broken wire in the communication harness

    Part replacement

    One or more of the wires on pins 1, 2, 7, 9, or 11 of the P20-to-J2 harness may be broken, chafed, or shorted. Inspect the full harness length for visible damage and check continuity at each relevant pin.

  3. 03

    Corroded or burnt connector pins

    Wiring / connection

    Heat and moisture in the oven cavity can cause oxidation or carbon buildup on the connector pins at P20 or J2, increasing resistance and degrading the communication signal. Inspect both connectors closely for discoloration or corrosion.

  4. 04

    Failed Appliance Control Board

    Part replacement

    If the harness and connectors check out, the Appliance Control Board itself may have failed and is no longer transmitting communication signals. This is a component-level failure that requires board replacement.

  5. 05

    Failed User Interface Board

    Part replacement

    Less commonly, the User Interface Board may have failed internally and cannot receive or interpret signals even when the ACB is transmitting correctly. This is typically diagnosed after ruling out harness and ACB issues.

See the test procedure for each cause

Frequently asked questions about F21

What does F21 mean on a Electrolux oven?
F21 indicates a communication problem between the User Interface Board and the Appliance Control Board. The User Interface Board is no longer detecting communication signals from the Appliance Control Board. The fault points to the communication harness running from connector P20 on the Appliance Control Board to connector J2 on the User Interface Board as the first area to inspect.
Can I fix the F21 error myself?
Some causes of F21 are DIY-accessible, such as reseating loose connectors or inspecting the harness for visible damage. You should disconnect power to the oven before handling any internal connectors or wiring. If the harness and connectors appear intact, diagnosing whether the Appliance Control Board or User Interface Board has failed typically requires a multimeter and some familiarity with control board testing, so professional service may be appropriate at that stage.
Is it safe to use my Electrolux oven while the F21 code is displayed?
It is not recommended to operate the oven while an F21 error is active. Because the two control boards cannot communicate, the oven may not respond correctly to user inputs or safety controls. You should avoid using the oven until the fault is diagnosed and resolved.
Will resetting the oven clear the F21 error?
Disconnecting power to the oven for several minutes and restoring it may temporarily clear the F21 code, but the error will return if the underlying communication fault is not corrected. A reset is useful for confirming whether the fault is intermittent, but it is not a repair. The harness and board connections should still be inspected.
How much does it cost to repair an F21 error on an Electrolux oven?
Repair costs vary depending on the root cause. If the issue is a loose connector or a replaceable harness, costs are typically lower, generally in the range of $50 to $150 for parts and labor. If the Appliance Control Board or User Interface Board requires replacement, costs can range from $150 to $400 or more depending on parts pricing and labor rates in your area.

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