Bosch Oven Error Code E303

E303 means the temperature sensor on the control module detected that the electronics are heating up too quickly, at a rate exceeding the programmed limit. In response, the oven shuts off all heating elements and switches the cooling fan to high speed to protect the control board. The fault points to a problem with the cooling fan, ventilation airflow, relay operation, or a heating element that is not cycling off correctly.

No, the oven should not be used while E303 is active. The control has already shut down the heating elements as a protective measure, and continuing to attempt operation without resolving the fault could cause damage to the control board. Address the cooling system and relay issues before resuming normal use.

Start by inspecting the wiring connections to the cooling fan and to the control module, using the Small Load Schematic for your specific model as a reference. Next, check that the cooling fan runs and that the upper and lower ventilation trim panels are undamaged and unobstructed. Verify that each heating element is cycling on and off correctly rather than staying energized, and check the relays to confirm none are stuck in the closed position.

Resetting the oven by cutting power at the breaker may clear E303 temporarily, but the fault will return if the underlying cause is not addressed. Because the code is triggered by a real thermal condition at the control module, resetting without inspection risks repeated thermal stress on the electronics. It is best to diagnose the cooling fan, ventilation path, and relay operation before attempting to use the oven again.

Repair costs depend on what component has failed. If only cleaning a blocked vent or reseating a loose connector resolves the issue, there may be no parts cost at all. A cooling fan motor replacement typically runs in the range of $50 to $150 for the part, while a control module replacement if the board was damaged by heat exposure can range from $150 to $400 or more. Professional labor adds to these estimates depending on your area.