Board Temperature Climbing Too Fast on a Bosch Oven: E303

What E303 means

This code tracks speed, not a single number. The sensor on the control module noticed the board warming up faster than Bosch permits, so the oven cut the heat and sent the cooling fan to maximum. As with the plain over-temperature code, heating comes back once the cavity falls to 212 degrees Fahrenheit, and self-clean remains locked out until the control is reset.

Common causes of E303

Cooling fan wearing out or spinning below speed
Air path above or below the door obstructed
Relay welded shut, delivering heat the control never requested

✓ One safe check you can try

1. While the oven is warm, listen for the cooling fan. 2. If it never starts, or sounds slower and rougher than before, that matches the first item technicians are asked to confirm. 3. Make sure nothing blocks the air gaps around the oven. 4. Tell us what you heard when you call.

! Why to stop there

The fan sits behind panels close to hot surfaces and live wiring.
A rising board temperature is a warning sign, and ignoring it can destroy the control module.
A weak fan and a stuck relay both cause this code, but the repairs are different.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

→Same appliance

Other Oven codes

E223Lower Probe Reads Colder Than Allowed (Bosch Oven E223) E226Bosch Oven E226 After the Lower Door Latch Signal Is Lost E314Bosch Oven E314 When the Cancel or Off Key Reads Stuck E414Off Key Failure Logged Behind the Scenes, Bosch Oven E414 E201Bosch Oven E201 on a Double Wall Model, Lower Cavity Sensor Reads Open E204Lower Sensor Wire Touching Metal: Bosch Oven E204 on Double Ovens E206Lower Oven Door Would Not Lock (Bosch Oven E206) E207Bosch Oven E207 and a Lower Cavity Door That Refuses to Unlock

E303E303 questions

How does this differ from E302?

E302 reacts to the board being too hot at one moment, and E303 reacts to it heating too quickly. Both lead to the same shutdown and need the same checks.

Is a slow fan something I can fix?

Cleaning dust near the vents may help, but a fan that is failing needs replacing. We test it on a visit and tell you before we change anything.

How serious is this?

Serious enough to stop the oven. Heat damage to the control module is costly, so it pays to inspect early. You see a written price first, and our repairs carry a 30-day workmanship warranty.