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Error code reference

Thermador Range Error Code F123

Keyboard disconnected, bad connection between keyboard and Display Board.

Thermador codesThermador range codes

Keyboard disconnected, bad connection between keyboard and Display Board.

First step from the service manual

Check all connections between keyboard (J1) and Display Board (P5). If OK, replace keyboard or Display Board or both.

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

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  • Wiring diagram references and connector pinouts from the OEM service manual
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What F123 means on a Thermador range

The F123 error code on a Thermador range indicates that the control system has detected a loss of communication between the keyboard (also called the keypad or touch panel) and the Display Board. These two components work together to accept user input and translate it into operational commands for the range. The connection between them runs through connector J1 on the keyboard side and connector P5 on the Display Board side. When the signal between these two points is interrupted or degraded, the Display Board cannot register keypad input and triggers the F123 fault.

The most common physical cause is a loose, corroded, or improperly seated connector at either J1 or P5. Ribbon cables and wire harnesses that carry the signal between these components can become dislodged through normal vibration during range operation, or may have been disturbed during a prior repair. In some cases, the connector itself may show signs of heat damage or oxidation that increases resistance at the contact point and breaks the communication signal.

If inspecting and reseating both connectors does not resolve the fault, the keyboard or the Display Board itself may have failed internally. A failed keyboard will not transmit any signal regardless of connector condition, while a failed Display Board will not recognize an otherwise functional keyboard signal. In some cases both components require replacement simultaneously, particularly if a power surge or overheating event damaged the communication circuit on both sides.

Source: manufacturer service documentation.

Common causes of F123

  1. 01

    Loose or unseated connector at J1 or P5

    Wiring / connection

    The ribbon cable or wire harness connecting the keyboard to the Display Board may have worked loose at connector J1 on the keyboard side or connector P5 on the Display Board side. Carefully inspecting and firmly reseating both connectors is the required first diagnostic step.

  2. 02

    Damaged or corroded connector contacts

    Part replacement

    Oxidation, heat exposure, or physical damage at the J1 or P5 connector pins can create a high-resistance or open circuit in the communication path. Inspect the contacts closely for discoloration, pitting, or bent pins.

  3. 03

    Failed keyboard assembly

    Part replacement

    The keyboard itself may have an internal failure that prevents it from transmitting any signal to the Display Board, even when the physical connection is intact. A failed keyboard will need to be replaced to restore communication.

  4. 04

    Failed Display Board

    Part replacement

    The Display Board may have suffered an internal failure on the communication circuit that prevents it from recognizing keyboard input through connector P5. If the keyboard checks out as functional, the Display Board is the next component to suspect.

  5. 05

    Damaged wiring harness between keyboard and Display Board

    Part replacement

    The wire harness or ribbon cable running between the two components may have a break, pinch, or chafed section that interrupts the signal. Visually trace the harness for any signs of physical damage.

See the test procedure for each cause

Frequently asked questions about F123

What does F123 mean on a Thermador range?
F123 indicates that the range has detected a disconnected or failed communication link between the keyboard and the Display Board. Specifically, the fault points to the connection at connector J1 on the keyboard and connector P5 on the Display Board. The range cannot accept keypad input when this error is active. The problem is either a loose connection or a failed keyboard or Display Board component.
Can I fix the F123 error on my Thermador range myself?
If the cause is simply a loose connector, a confident DIYer comfortable working with appliance electronics can reseat the connections at J1 and P5 after disconnecting power to the range. However, if the keyboard or Display Board itself has failed, replacing those components requires correctly identifying the right parts and handling the electronics carefully. If you are not comfortable with appliance disassembly and electrical components, a qualified technician is the safer choice.
Will resetting the range clear the F123 error code?
A power reset by turning off the circuit breaker for one to two minutes may temporarily clear the error display, but if the underlying connection problem or component failure still exists, the F123 code will return. A reset is useful for confirming whether the fault is intermittent, but it does not fix a loose connector, damaged wiring, or failed keyboard or Display Board.
Is it safe to use my Thermador range when the F123 error is showing?
The F123 error indicates a loss of keyboard communication, which means the control panel may not respond correctly to input. Operating the range in this condition is not recommended because you may not be able to reliably control cooking functions or cancel operations. Disconnect power and address the fault before resuming normal use.
How much does it cost to repair a Thermador range with an F123 error?
If the fix is simply reseating a connector, the cost is limited to a service call fee, which typically ranges from around 75 to 150 dollars depending on your area. If the keyboard requires replacement, parts and labor generally run between 150 and 350 dollars. Replacing the Display Board tends to be the more expensive repair, often ranging from 250 to 500 dollars or more, and replacing both components simultaneously will increase the total cost accordingly.

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