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Error code reference

Thermador Oven Error Code E123

Upper/single cavity (Cvt 1) probe sensor temperature too low.

Thermador codesThermador oven codes

Upper/single cavity (Cvt 1) probe sensor temperature too low.

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What E123 means on a Thermador oven

Error code E123 on a Thermador oven indicates that the probe sensor in the upper or single cavity (designated as Cavity 1 or Cvt 1) is reading a temperature that is abnormally low. This is a meat probe or temperature probe fault, meaning the oven's control board is detecting a signal from the probe circuit that falls below the expected threshold for normal operation. The control interprets this as either an open circuit, a shorted sensor, or a probe that is not properly connected, and it halts normal cooking operation to prevent inaccurate temperature monitoring.

The probe sensor circuit works by sending a reference voltage through the probe and reading the returned signal to calculate the temperature at the probe tip. When the returned value drops too low, the control board flags E123 to alert the user and technician that something in that circuit has failed. Common points of failure include the probe itself, the probe receptacle jack inside the oven cavity, or the wiring harness that runs between the receptacle and the control board.

In some cases, the error can be triggered simply by a probe that is partially inserted into the wall receptacle or one that has been damaged by heat or physical stress. A corroded or burned receptacle jack is also a frequent culprit, particularly in ovens that have seen heavy use. If no probe is physically connected and the oven is still generating this code, the receptacle or the wiring circuit tied to it is the likely source of the fault.

Source: manufacturer service documentation.

Common causes of E123

  1. 01

    Faulty or damaged probe sensor

    Part replacement

    The meat probe itself can fail due to heat stress, physical damage, or internal wire breakage. Inspect the probe cable for kinks, burns, or visible damage and test the probe for continuity.

  2. 02

    Probe not fully seated in the receptacle

    Wiring / connection

    A partially inserted probe can cause a low or erratic signal reading. Remove and firmly reinsert the probe into the oven wall receptacle to ensure a solid connection.

  3. 03

    Corroded or burned probe receptacle jack

    Part replacement

    The receptacle port inside the oven cavity can corrode, oxidize, or sustain heat damage over time, leading to a poor electrical connection. Visually inspect the jack for discoloration, debris, or bent contacts.

  4. 04

    Damaged wiring harness between receptacle and control board

    Part replacement

    The wiring that connects the probe receptacle to the oven control board can suffer insulation damage or loose connector terminals, producing a low-signal fault. Inspect the harness for heat damage or disconnected terminals.

  5. 05

    Failed oven control board

    Part replacement

    If the probe, receptacle, and wiring all test within normal parameters, the control board itself may be misreading the probe circuit signal. This is the least common cause and should be diagnosed only after all other components are ruled out.

See the test procedure for each cause

Frequently asked questions about E123

What does E123 mean on a Thermador oven?
E123 indicates that the probe sensor temperature in the upper or single oven cavity (Cvt 1) is reading too low, signaling a fault in the probe circuit. This means the control board is receiving a signal that falls below the expected range, which can point to a failed probe, a bad receptacle connection, or a wiring issue. The oven displays this code to prevent cooking operations from proceeding with inaccurate temperature data.
Can I fix the E123 error myself on a Thermador oven?
Some causes of E123 are DIY-friendly, such as reseating the probe in the receptacle or replacing a visibly damaged probe. However, diagnosing a faulty receptacle jack, damaged wiring harness, or control board issue typically requires disassembly of the oven and familiarity with electrical testing. If you are not comfortable working with appliance wiring, a qualified technician should handle the repair.
Will resetting the oven clear the E123 error code?
A power reset by turning off the oven at the circuit breaker for a few minutes may temporarily clear the E123 code, but if the underlying fault in the probe circuit remains, the error will return. Resetting is useful to confirm whether the fault is intermittent or persistent, but it does not repair a damaged probe, receptacle, or wiring.
Is it safe to use my Thermador oven when E123 is displayed?
It is not recommended to use the oven for probe-guided cooking when E123 is active, because the temperature readings from the probe circuit cannot be trusted. Standard baking or roasting without the probe connected may still be possible depending on how the oven responds to the fault, but continuing to operate with an unresolved probe circuit issue could result in improperly cooked food or further component damage.
How much does it cost to repair a Thermador oven showing E123?
Repair costs vary depending on the failed component. A replacement probe sensor typically runs in the range of $30 to $80 for the part alone. A probe receptacle jack or wiring harness repair may cost $100 to $250 in parts and labor combined. If the control board is the source of the fault, that repair can range from $300 to $600 or more depending on parts availability and labor rates in your area.

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