Thermador Oven Error Code E123

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.

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.

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.

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.

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.