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Error code reference

Bosch Microwave Error Code E17

Preheat fail

Bosch codesBosch microwave codes

Preheat fail — oven did not reach target temperature within 15 minutes.

First step from the service manual

If detected, unit reverts to clock mode; display shows error code for 3 seconds. Check heating elements and thermistor.

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

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
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What E17 means on a Bosch microwave

The E17 error code on a Bosch microwave indicates a preheat failure, meaning the oven cavity did not reach its programmed target temperature within the 15-minute preheat window. This code is specific to combination microwave-oven units that include convection or grill heating capability. When the control board monitors the preheat cycle, it continuously compares the thermistor's reported temperature against the target setpoint. If that setpoint is not achieved within the allotted 15 minutes, the control board triggers E17, displays the code for 3 seconds, and then reverts the unit to clock mode as a failsafe.

The two primary components implicated in this fault are the heating element and the thermistor. The heating element is responsible for generating the thermal energy needed to bring the cavity up to temperature. A failed or degraded element will produce insufficient heat, making it impossible to reach the setpoint in time. The thermistor acts as the temperature sensor, reporting cavity temperature back to the control board. A thermistor that reads incorrectly, whether due to a drift in resistance or a broken connection, can cause the board to believe the target was never met even when heating is otherwise normal.

Additional contributing factors can include a malfunctioning control board that fails to properly drive the heating circuit, poor door seal integrity causing heat loss, or a blocked or restricted ventilation path that prevents accurate thermal buildup. Because the unit reverts to clock mode after displaying E17, the appliance is non-operational for cooking until the underlying fault is resolved. Technicians should begin by inspecting the heating element for visible damage and testing the thermistor for proper resistance values before moving to control board diagnostics.

Source: manufacturer service documentation.

Common causes of E17

  1. 01

    Failed heating element

    Part replacement

    A burnt-out or degraded heating element cannot generate enough heat to reach the target temperature within the 15-minute window. Inspect the element visually for breaks, blistering, or burn marks, and test for continuity.

  2. 02

    Faulty thermistor

    Part replacement

    A thermistor that has drifted out of its correct resistance range will report inaccurate cavity temperatures to the control board, triggering E17 even if the element is functioning. Test the thermistor's resistance and compare it against the specified value for the unit.

  3. 03

    Poor door seal or gasket

    Part replacement

    A damaged or worn door seal allows heat to escape the cavity during preheat, slowing temperature rise enough to exceed the 15-minute limit. Inspect the door gasket for tears, compression loss, or gaps around the perimeter.

  4. 04

    Restricted or blocked ventilation

    Wiring / connection

    Blocked vents can interfere with proper thermal circulation inside the cavity, preventing the temperature from climbing at a normal rate. Check all intake and exhaust vents for obstructions such as grease buildup or debris.

  5. 05

    Control board fault

    Part replacement

    If the control board is not properly driving the heating circuit, the element may receive insufficient power to heat the cavity. This is typically diagnosed after the heating element and thermistor have been confirmed to be in good working order.

See the test procedure for each cause

Frequently asked questions about E17

What does E17 mean on a Bosch microwave?
E17 on a Bosch microwave means the oven failed to reach its target temperature within 15 minutes during a preheat cycle. The control board monitors temperature through the thermistor throughout the preheat window and triggers this code when the setpoint is not met in time. After displaying the code for 3 seconds, the unit reverts to clock mode and will not operate for cooking until the fault is corrected. The most likely causes are a failed heating element or a faulty thermistor.
Can I fix the E17 error on my Bosch microwave myself?
Some steps, such as checking for blocked vents or inspecting the door seal, can be done without specialized tools. However, testing the thermistor resistance and inspecting or replacing the heating element involves working inside the appliance, which carries electrical hazard risks. If you are not comfortable working around high-voltage components, a qualified appliance technician should perform the repair. Always unplug the unit before opening the cabinet.
Is it safe to use my Bosch microwave when E17 is displayed?
No. When E17 is triggered, the unit automatically reverts to clock mode and cooking functions are disabled. Attempting to bypass this state without resolving the underlying fault is not recommended, as the heating system is not operating correctly. The appliance should remain unplugged until the cause of the preheat failure is identified and repaired.
Will resetting my Bosch microwave clear the E17 error?
Unplugging the unit or performing a power reset may clear the displayed code temporarily, but it will not resolve the underlying hardware fault. If the heating element or thermistor is defective, the error will return as soon as another preheat cycle is attempted. A reset is useful only for ruling out a transient control board glitch, not as a permanent fix.
How much does it cost to repair a Bosch microwave showing E17?
Repair costs vary depending on which component has failed. A replacement thermistor is generally a lower-cost part, while a heating element or control board replacement will cost more, particularly when labor is included. Total repair costs, including parts and professional labor, typically range from around $100 to $350 or more depending on the specific part needed and local labor rates. Getting a diagnostic estimate from a technician before committing to the repair is a good approach.

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