When this error occurs, you will likely notice the oven operation abruptly halting. The cooling fan may run at maximum velocity in an attempt to dissipate the excess heat, or conversely, you might hear an eerie silence if the fan motor has failed. The display will flash “E115,” and the oven may refuse to restart even after a manual power cycle. Don’t worry—while this sounds intimidating, it is a protective measure. In most cases, it is caused by a faulty sensor or an airflow obstruction rather than a catastrophic failure of the heating elements.
Symptoms of Bosch Error E115
As a senior engineer, I categorize the symptoms of E115 into three distinct observational phases. Identifying these can help narrow down whether the issue is a “ghost” reading or a legitimate overheating event.
⚠️ Warning: Check Manual First
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- The Control Freeze: The oven display will stop showing the current time or temperature and lock onto the E115 code. Often, the buttons or touch interface will become unresponsive as the system enters “Safe Mode.”
- Aggressive Cooling Fan Activity: You may hear the upper cooling fan (located behind the control panel, not the convection fan in the back) running at an unusually high pitch or continuing to run for hours after the oven has been turned off.
- Thermal Cut-out Activation: If the temperature was truly excessive, the oven may lose all power suddenly. This happens when the manual-reset thermal limiter trips to cut the line voltage.
- Incomplete Cooking Cycles: The oven may work fine for 15-20 minutes but throw the E115 code once it reaches higher temperatures (e.g., above 400°F), indicating a sensor that is “drifting” out of its resistance range.
The Complete Solution
The Complete Solution: Step-by-Step Fix
Follow these steps in order. Always prioritize safety when working with high-voltage appliances.
Step 1: The Hard Reset (Capacitor Discharge).
Before dismantling the unit, turn off the circuit breaker for at least 10 minutes. This allows the capacitors on the control board to fully discharge and resets the microprocessor’s error memory. Sometimes, a voltage spike on the grid can cause a “nuisance trip” of the E115 code. If the code returns immediately upon powering back up, proceed to Step 2.
Step 2: Access and Safety.
WARNING: Ensure the power is OFF. Verify with a non-contact voltage tester. Slide the oven out of its housing (you may need to unscrew two T20 Torx screws located on the side trim when the door is open). Remove the top panel to gain access to the cooling fan and the rear panel to access the NTC sensor wiring.
Step 3: Test the NTC Temperature Sensor.
Locate the temperature probe inside the oven (usually top right or left corner). Follow the wires to the back of the oven. Disconnect the plastic harness. Set your multimeter to the Ohms (Ω) setting. At room temperature (approx. 75°F/25°C), the sensor should read approximately 10k to 11k ohms. If it reads “OL” (Open Loop) or significantly lower than 5k at room temperature, the sensor is faulty and must be replaced. Replace it by unscrewing the single screw inside the oven cavity and pulling the probe through.
Step 4: Inspect the Cooling Blower.
Spin the cross-flow fan (the long cylindrical fan) by hand. It should spin freely with no resistance. If it feels “crunchy” or stiff, clean any grease buildup with a soft brush and vacuum. If the fan moves freely but didn’t run during the oven’s operation, check for 120V (or 240V depending on your model) at the fan terminals using your multimeter while the oven is on (be extremely careful). If power is present but the fan is stagnant, replace the blower motor.
Step 5: Inspect the Power Module.
If the sensor and fan are perfect, inspect the main control board for dark scorch marks around the relays. A stuck relay will often show signs of heat damage on the circuit board itself. If you find localized burning, the entire power module usually requires replacement, as these components are typically not serviced at the component level in the field.
Quick Repair Specifications
| Repair Difficulty: | Intermediate (Requires electrical testing) |
| Estimated Time: | 45 – 90 Minutes |
| Tools Needed: | Digital Multimeter, Torx T20 Screwdriver, Needle-nose Pliers, Soft Bristle Brush |
| Estimated Cost: | $20 (Sensor) to $250 (Control Board) |
Technical Explanation of the Fault
To fix E115, we must understand the engineering behind the thermal monitoring system. The Bosch control module relies on a constant feedback loop to ensure the oven environment remains stable. When this loop is broken, the E115 error is thrown.
1. NTC Thermistor Resistance Drift: Bosch ovens use a Negative Temperature Coefficient (NTC) sensor. As the temperature rises, the electrical resistance of the sensor drops. Over time, moisture or microscopic cracks in the ceramic casing of the sensor can cause “resistance drift.” The sensor might report a resistance level that translates to 600°F when the oven is actually only 350°F. The logic board sees this “implausible” data and triggers E115.
2. Cooling Fan Motor Impedance: The cooling fan (cross-flow blower) is responsible for pulling heat away from the sensitive electronic control board. If the motor bearings become dry or the fan blades are clogged with kitchen grease, the fan RPM drops. The heat then builds up around the control board’s internal temperature sensor, leading the oven to believe the *cavity* is overheating, even if the food is cold.
3. Stuck Control Board Relay: In rare cases, the mechanical relay on the power module that controls the heating element can “weld” shut due to electrical arcing. This keeps the heating element energized indefinitely, regardless of what the thermostat says. This is a genuine overheating scenario where the safety software intervenes to prevent a fire.
How to Prevent Error E115
Prevention is centered around maintaining optimal airflow and electrical stability. These three tips will significantly extend the life of your Bosch oven’s sensors and boards.
- Maintain Cabinet Clearances: Ensure your oven was installed with the manufacturer-specified “air gap” at the rear and bottom. Bosch ovens are designed to pull cool air from the bottom and exhaust hot air through the vent above the door. If the cabinetry is too tight, the heat will soak into the electronics, causing E115.
- Degrease the Cooling Vents: Every six months, use a vacuum attachment to suck out dust and grease from the vent intake (usually located under the control panel). Dust acts as an insulator; if it coats the control board, the board cannot shed heat, leading to premature thermal failure.
- Use Pyrolytic Cleaning Sparingly: The self-cleaning cycle subjects the oven to temperatures exceeding 900°F. While the oven is designed for this, it is the #1 cause of NTC sensor failure and thermal fuse trips. If you must use it, ensure the kitchen is well-ventilated and the oven has plenty of space to breathe.
Frequently Asked Questions
Q: Can I bypass the sensor to keep cooking?
A: Absolutely not. The E115 error is a safety protocol. Bypassing thermal sensors or limiters is a major fire hazard. If the oven is actually overheating, it could melt the control wiring or damage your kitchen cabinets.
Q: My oven door is locked and won’t open after E115 appeared. What do I do?
A: This is a safety feature to prevent you from being burned by a potential flash-fire if the oven is excessively hot. Allow the oven to cool for at least 2 hours. Once the NTC sensor detects a safe temperature, the latch should automatically retract. If it doesn’t, you may need to perform a power reset at the breaker.
Q: Is Error E115 the same as E118?
A: No, while they both relate to temperature, E118 usually points specifically to a communication error between the power module and the display, whereas E115 is strictly regarding a thermal limit being exceeded in the cavity or at the board.