Thermador Oven Error Code E303

E303 on a Thermador oven means the control module electronics have exceeded 212°F (100°C). The oven shuts down to protect the control board from heat damage. This fault is triggered by a thermal threshold built into the control system. Common causes include blocked ventilation, a failed cooling fan, or an overheating oven cavity.

You should not continue operating the oven while E303 is active. The fault indicates the control electronics are being exposed to unsafe heat levels, and continued use risks permanent damage to the control board. Allow the oven to cool completely and investigate the cause before attempting to use it again.

Repair costs vary depending on the root cause. Clearing a blocked vent costs nothing beyond your time, while replacing a cooling fan typically runs in the range of $100 to $300 including parts and labor. A full control board replacement on a Thermador oven can range from $300 to $700 or more depending on the model and service rates in your area.

Some causes of E303 are DIY-friendly, such as clearing blocked vents or improving installation clearances around the oven. However, diagnosing and replacing a failed cooling fan, temperature sensor, or control board typically requires disassembling internal panels and working with electrical components, which is better suited to a qualified appliance technician.

Resetting the oven by cutting power at the breaker for several minutes may temporarily clear E303, but the fault will return if the underlying cause is not resolved. If the electronics are overheating due to a blocked vent or failed fan, the code will reappear during or after the next cooking cycle. A reset alone is not a repair.