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Error code reference

Thermador Range Error Code F40

Upper meat probe shorted.

Thermador codesThermador range codes

Upper meat probe shorted.

First step from the service manual

Check header P2 on the control display PCB. Check that neither meat probe wire is pinched to chassis. If F40 persists, replace the control display PCB.

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

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What F40 means on a Thermador range

The F40 error code on a Thermador range indicates that the upper meat probe circuit has detected a short condition. The meat probe is a temperature-sensing accessory that plugs into the oven cavity to monitor internal food temperature during cooking. When the control system reads an abnormally low resistance across the probe circuit, it interprets this as a short and triggers the F40 fault. A properly functioning probe presents a specific resistance value to the control board; a shorted circuit collapses that resistance toward zero ohms, which the board flags as a fault condition.

The control display PCB is the central component in diagnosing this fault. Header P2 on this board is the specific connector where the upper meat probe wiring terminates, and it is the first point of inspection. The wiring harness that connects the probe jack in the oven cavity to this header runs through or along the range chassis, and if any section of wire is pinched between metal panels or chassis components, insulation can be compromised and cause a direct short to ground or between the two probe wires.

Common causes include a damaged meat probe itself, pinched or chafed wiring along the harness route, a faulty connection at header P2, or a failed control display PCB. Because the diagnostic path moves from wiring inspection to board replacement, technicians should thoroughly trace the full harness length before condemning the PCB. If the wiring and connections check out and the fault persists without any probe inserted, the control display PCB is likely the source of the fault and will need to be replaced.

Source: manufacturer service documentation.

Common causes of F40

  1. 01

    Damaged or faulty meat probe

    Part replacement

    The meat probe itself can develop an internal short if the cable is kinked, the tip is damaged, or the connector is corroded. Try unplugging the probe and checking whether the F40 code clears.

  2. 02

    Pinched meat probe wiring harness

    Wiring / connection

    The wiring that runs from the probe jack inside the oven cavity to header P2 on the control board can become pinched against the chassis during servicing or over time. Inspect the full length of the harness for any areas where insulation has been cut or compressed by metal edges.

  3. 03

    Loose or corroded connection at header P2

    Wiring / connection

    Header P2 on the control display PCB is the termination point for the upper meat probe circuit. A loose, corroded, or improperly seated connector at this header can create a false short reading.

  4. 04

    Failed control display PCB

    Part replacement

    If the wiring and probe connections are all intact and the fault persists, the control display PCB itself may have an internal failure causing it to misread the probe circuit as shorted. Board replacement is the indicated repair at that point.

See the test procedure for each cause

Frequently asked questions about F40

What does F40 mean on a Thermador range?
F40 on a Thermador range means the control system has detected a short in the upper meat probe circuit. The board monitors the resistance of the probe wiring and flags this code when resistance drops to an abnormal level. This can be caused by a damaged probe, pinched wiring, or a faulty control display PCB. The first step is to inspect header P2 on the control display PCB and check that no meat probe wires are pinched against the chassis.
Can I fix the F40 error myself, or do I need a technician?
Some steps are accessible to a knowledgeable DIYer. You can unplug the meat probe and check whether the code clears, and you can visually inspect the probe wiring for obvious damage or pinching. However, inspecting header P2 on the control display PCB and replacing the board if needed requires disassembling part of the range and working near live components, which is better handled by a qualified appliance technician.
Is it safe to use my Thermador range while F40 is showing?
An F40 code indicates a shorted probe circuit, which means the meat probe temperature monitoring system is not functioning correctly. If the probe feature is not needed for your immediate cooking task, the range may still operate, but it is best to resolve the fault promptly. Continuing to use the appliance with an undiagnosed wiring short is not recommended without first confirming the source of the short.
Will resetting the range clear the F40 error code?
A power reset by turning off the breaker for 60 seconds may temporarily clear the display, but F40 will return if the underlying fault in the probe circuit is still present. The code is tied to an active hardware condition, so it will not stay cleared until the shorted wiring, damaged probe, or faulty PCB is repaired or replaced.
How much does it cost to repair a Thermador range F40 error?
Repair costs vary depending on the root cause. If the meat probe itself is shorted and needs replacement, costs are generally in the range of $30 to $80 for the part plus labor. If the control display PCB is the cause, parts alone can range from $150 to $400 or more depending on the model, with additional labor costs on top of that. Getting a diagnostic visit from a technician first will help determine which component is at fault before committing to parts.

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