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Error code reference

Bosch Range Error Code E303

Electronics Delta temperature too high

Bosch codesBosch range codes

Electronics Delta temperature too high — temperature sensor on the control module detects temperature changes that over time are higher than limit value; control turns off heating elements and fan defaults to high speed.

First step from the service manual

Check connections to cooling fan and to control module (see Small Load Schematic). Check element operation. Check for air obstruction or damaged upper/lower ventilation trims. Check for stuck relays.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What E303 means on a Bosch range

The E303 error code on a Bosch range indicates that the electronics delta temperature has exceeded its acceptable limit. The temperature sensor located on the control module monitors the rate of temperature change over time within the control electronics compartment. When the rate of rise exceeds the programmed threshold, the control interprets this as a thermal overload condition in the electronics bay. In response, the control automatically shuts off the heating elements to prevent further heat generation and forces the cooling fan to run at high speed in an attempt to bring temperatures back into a safe range.

This fault is specifically about the thermal environment surrounding the control module, not the oven cavity temperature itself. The cooling fan plays a central role in this system. If the fan is not running at proper speed, is obstructed, or has failed entirely, heat will accumulate around the electronics faster than normal and trigger E303. Similarly, blocked ventilation trims at the top or bottom of the range prevent airflow from moving through the electronics compartment effectively.

Stuck relays are another documented cause. A relay that is stuck in the closed position can cause a heating element to run continuously, generating excess heat in the electronics area even when the oven is not actively in a cook cycle. Wiring connection issues at the fan or the control module itself can also cause the fan to operate intermittently or not at all, resulting in the same thermal accumulation that triggers this fault.

Source: manufacturer service documentation.

Common causes of E303

  1. 01

    Cooling fan failure or poor connection

    Part replacement

    If the cooling fan is not running or is running at reduced speed due to a wiring fault or failed motor, heat builds up around the control module and triggers E303. Check the electrical connections to the fan and verify the fan spins freely and operates at full speed.

  2. 02

    Blocked or damaged ventilation trims

    Part replacement

    The upper and lower ventilation trims direct airflow through the electronics compartment. If these are physically blocked by debris or are damaged and restricting airflow, the electronics bay will overheat. Inspect both trims for obstructions, cracks, or deformation.

  3. 03

    Stuck relay on the control module

    Part replacement

    A relay stuck in the closed position can cause a heating element to run continuously, pushing heat into the electronics area beyond normal operating levels. Check each relay for proper operation and listen for audible clicking when the control cycles.

  4. 04

    Loose or corroded connections at the control module

    Wiring / connection

    Poor connections at the control module can cause the cooling fan circuit to behave intermittently, reducing cooling effectiveness. Inspect all wiring harness connectors at the control module and the fan, referencing the Small Load Schematic for the correct terminals.

  5. 05

    Heating element drawing excessive current

    Part replacement

    A shorted or malfunctioning heating element can generate abnormal heat output that overwhelms the cooling system. Check element operation and verify the element is cycling off correctly during normal use.

See the test procedure for each cause

Frequently asked questions about E303

What does E303 mean on a Bosch range?
E303 means the temperature sensor on the control module detected that the electronics compartment temperature rose too quickly over time, exceeding the programmed limit. The control responds by shutting off all heating elements and running the cooling fan at high speed to protect the control electronics. This is a thermal protection fault specific to the electronics bay, not the oven cavity itself.
Can I fix E303 on my Bosch range myself?
Some causes of E303 are DIY-accessible, such as clearing blocked ventilation trims or reseating loose wiring connectors at the fan and control module. However, diagnosing a stuck relay, a failed cooling fan motor, or a faulty heating element typically requires a multimeter and comfort working inside the appliance. If you are not experienced with appliance electrical systems, a qualified technician is recommended.
Is it safe to use my Bosch range while E303 is displayed?
No. When E303 is active, the range has already disabled the heating elements as a protective measure. Attempting to bypass this condition or continue cooking before the underlying cause is resolved could result in damage to the control board or a potential safety hazard. The range should remain out of service until the fault is diagnosed and corrected.
Will resetting the Bosch range clear the E303 error code?
A power reset by turning off the circuit breaker for several minutes may clear the fault temporarily if the electronics have cooled down, but E303 will return if the root cause is not addressed. A reset should be used only as part of diagnostics, not as a fix. Persistent or recurring E303 codes indicate a component issue that requires repair.
How much does it cost to repair a Bosch range showing E303?
Repair costs vary depending on the failed component. A replacement cooling fan motor typically falls in the range of $50 to $150 for the part alone. A new control module can range from $150 to $400 or more depending on the model. Labor costs from an appliance technician typically add $100 to $200 depending on your region and the complexity of the repair.

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