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Error code reference

Bosch Refrigerator Error Code E31

Icemaker tray or water tank temperature sensor defect.

Bosch codesBosch refrigerator codes

Icemaker tray or water tank temperature sensor defect.

First step from the service manual

Check the icemaker sensor and water tank sensor; resistance of icemaker tray sensor at 25°C should be about 10kΩ, water tank sensor at 25°C should be about 5kΩ.

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

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What E31 means on a Bosch refrigerator

The E31 error code on a Bosch refrigerator indicates a defect detected in one or both of the temperature sensors associated with the icemaker system: specifically the icemaker tray sensor or the water tank sensor. These sensors are negative temperature coefficient (NTC) thermistors that continuously monitor temperatures in their respective locations and feed that data to the control board. The control board uses these readings to manage the ice-making cycle, including when to freeze, harvest, and refill.

The primary diagnostic benchmark is resistance measurement at a known temperature. At 25°C, the icemaker tray sensor should read approximately 10kΩ, while the water tank sensor should read approximately 5kΩ. A reading that falls significantly outside these values, or an open/short circuit condition, will trigger E31. Causes include sensor failure due to age or moisture intrusion, damaged wiring or connectors between the sensor and control board, or a harness that has been pinched or corroded.

Because these two sensors have different nominal resistance values, the control board can distinguish between them, but both faults register under the same E31 code. A technician should test each sensor individually using a multimeter set to resistance mode, comparing the measured value against the specified 10kΩ or 5kΩ baseline. Wiring continuity between each sensor and the control board should also be confirmed before replacing any component.

Source: manufacturer service documentation.

Common causes of E31

  1. 01

    Failed icemaker tray sensor

    Part replacement

    The icemaker tray NTC thermistor has drifted out of specification or failed entirely. At 25°C, a working sensor reads approximately 10kΩ; a reading well above or below this value, or an open circuit, confirms failure.

  2. 02

    Failed water tank sensor

    Part replacement

    The water tank NTC thermistor has failed or drifted beyond acceptable tolerance. At 25°C it should measure approximately 5kΩ; deviations or an open/short circuit indicate the sensor needs replacement.

  3. 03

    Damaged or corroded wiring harness

    Wiring / connection

    The wiring between either sensor and the control board may be pinched, broken, or corroded at a connector. Inspecting the harness visually and testing continuity with a multimeter can isolate this before replacing sensors.

  4. 04

    Loose or disconnected sensor connector

    Wiring / connection

    A connector that has worked loose due to vibration or ice buildup can cause the control board to read an open circuit and trigger E31. Reseating the connector firmly may resolve the code.

  5. 05

    Moisture or ice intrusion at the sensor

    Wiring / connection

    Water or ice accumulation around a sensor's connector can cause intermittent or permanent resistance shifts. Defrosting the icemaker compartment fully and inspecting for moisture damage at sensor contact points is recommended.

See the test procedure for each cause

Frequently asked questions about E31

What does E31 mean on a Bosch refrigerator?
E31 indicates a defect in the icemaker tray temperature sensor or the water tank temperature sensor. These are NTC thermistors that the control board monitors to manage the ice-making cycle. The fault is confirmed by measuring sensor resistance, which should be approximately 10kΩ for the tray sensor and 5kΩ for the water tank sensor at 25°C. If either reading is significantly off or shows an open or short circuit, the sensor or its wiring is the source of the code.
Can I fix E31 on my Bosch refrigerator myself?
A knowledgeable DIYer can diagnose E31 by testing sensor resistance with a multimeter and inspecting the wiring harness and connectors for damage. If a connector is simply loose, reseating it may clear the code without parts. Replacing the faulty sensor is also a manageable repair for someone comfortable working with appliance electronics, but if the control board itself is suspected, professional service is advisable.
Is it safe to use my refrigerator while E31 is active?
The main refrigerator and freezer compartments typically continue operating normally while E31 is active, so food safety is generally not at immediate risk. However, the icemaker may stop producing ice or behave erratically until the sensor fault is resolved. It is best to address the repair promptly to prevent any secondary issues with the icemaker system.
How much does it cost to repair a Bosch E31 error?
If the fix is a loose connector, there may be no parts cost at all. Replacing an icemaker tray or water tank sensor typically involves parts costs in the range of $20 to $80 depending on the specific sensor and source. If professional labor is needed, total repair costs including diagnosis and installation commonly fall in the range of $100 to $250.
Will resetting my Bosch refrigerator clear the E31 code?
A power reset may temporarily clear the E31 code from the display, but if the underlying sensor or wiring fault still exists, the code will return once the control board runs its diagnostic check again. A reset is useful for confirming whether the fault is intermittent, but it is not a substitute for diagnosing and correcting the actual sensor or wiring problem.

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