Bosch Smart Thermostats Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E01
Thermostat display shows E01 and cannot connect to the Bosch server or Bosch HomeCom Easy / HomeCom Pro app.
Cloud Connectivity Failure
E02
Thermostat shows E02 and cannot join the Wi‑Fi network during setup.
Wi‑Fi Association Failure
E03
Thermostat displays E03 and cannot detect the indoor temperature sensor; temperature reading is blank or shows dashes.
Internal Temperature Sensor Failure
E04
Thermostat shows E04 and reports an external room sensor fault when using a remote Bosch NTC room sensor.
Remote Room Sensor Circuit Open/Short
E05
Thermostat displays E05 and indicates a floor sensor error (for hydronic or radiant floor applications).
Floor Temperature Sensor Fault
E06
Thermostat shows E06 and heating or cooling does not start; internal relay or triac fault indicated.
Output Relay/Triac Failure
E07
Thermostat displays E07 and shows no outdoor temperature; weather‑dependent functions disabled.
Outdoor Sensor / Weather Data Failure
E08
Thermostat shows E08 and reports low supply voltage; display may dim or reboot intermittently.
Low 24 V Control Voltage
E09
Thermostat displays E09 and cannot detect a required C‑wire; device may run only on batteries or not power up fully.
Missing or Unstable Common (C) Wire
E10
Thermostat shows E10 and indicates communication loss with Bosch boiler or heat pump over BUS/eBUS/EMS interface.
Digital BUS Communication Failure
E11
Thermostat displays E11 and indicates an internal memory or configuration error; settings may not save.
Non‑Volatile Memory (NVM) Corruption
E12
Thermostat shows E12 and touchscreen or buttons do not respond properly.
User Interface / Touch Panel Failure
E13
Thermostat displays E13 and indicates an internal temperature over‑limit; device may shut down temporarily.
Thermostat Overtemperature Protection
E14
Thermostat shows E14 and indicates a humidity sensor error; humidity reading is missing or unrealistic.
Internal Humidity Sensor Failure
E15
Thermostat displays E15 and indicates a schedule or clock synchronization error; timed programs may not run correctly.
Real‑Time Clock / Time Sync Failure
E16
Thermostat shows E16 and indicates a firmware update failure; device may be stuck on an update screen.
Firmware Update Interruption
E17
Thermostat displays E17 and indicates an internal sensor calibration error; temperature readings may be offset.
Internal Sensor Calibration Fault
E18
Thermostat shows E18 and indicates a geofencing/location service error; away/home automation not functioning.
Geolocation Service Failure
E19
Thermostat displays E19 and indicates an incompatible HVAC system configuration detected.
System Configuration Mismatch
E20
Thermostat shows E20 and indicates a security/authentication error with Bosch cloud services.
Cloud Authentication Failure
Symptom
Cooling runs but thermostat overshoots setpoint and room becomes too cold before shutting off.
Cooling Overshoot / Poor Temperature Control
Symptom
Heating runs but thermostat overshoots setpoint and room becomes too warm before shutting off.
Heating Overshoot / Poor Temperature Control
Symptom
Thermostat backplate or surrounding wall feels unusually warm to the touch.
Localized Overheating at Thermostat
Symptom
Thermostat calls for heat but Bosch boiler or furnace does not start; indicator shows heating demand active.
Heat Demand Not Reaching Equipment
Symptom
Thermostat cannot be added to Bosch smart home ecosystem or third‑party integrations (e.g., voice assistants) fail.
Integration / Pairing Failure
Symptom
Thermostat display is completely blank and does not power on.
No Power to Thermostat
Symptom
Thermostat does not call for cooling even when room is warm and setpoint is lower than room temperature.
No Cool Call from Thermostat
Symptom
Thermostat does not respond to Bosch app commands when away from home, but works locally.
Remote Access Failure
Symptom
Thermostat does not turn on the fan in ON mode, but fan runs during heating or cooling.
Fan Only Mode Not Working
Symptom
Thermostat fails to follow programmed schedule; heating/cooling does not change at scheduled times.
Schedule Execution Failure
Symptom
Thermostat frequently cycles the HVAC system on and off in short bursts (short cycling).
Short Cycling Due to Control Settings or Sizing
Symptom
Thermostat frequently disconnects from Wi‑Fi and goes offline in the Bosch app.
Intermittent Wi‑Fi Connectivity
Symptom
Thermostat is very slow to respond to touch or app commands; menus lag or freeze.
Performance Degradation / Software Lag
Symptom
Thermostat powers on but does not call for heat even when room is cold and setpoint is higher than room temperature.
No Heat Call from Thermostat
Symptom
Thermostat reboots randomly or the screen flickers during operation.
Unstable Power or Internal Reset
Symptom
Thermostat shows incorrect room temperature compared to other thermometers.
Temperature Reading Inaccuracy
Symptom
Thermostat shows large swings in humidity readings or humidity control is erratic.
Humidity Measurement or Control Instability
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E01 |
Thermostat display shows E01 and cannot connect to the Bosch server or Bosch HomeCom Easy / HomeCom Pro app.
|
Cloud Connectivity Failure | View Details |
| E02 |
Thermostat shows E02 and cannot join the Wi‑Fi network during setup.
|
Wi‑Fi Association Failure | View Details |
| E03 |
Thermostat displays E03 and cannot detect the indoor temperature sensor; temperature reading is blank or shows dashes.
|
Internal Temperature Sensor Failure | View Details |
| E04 |
Thermostat shows E04 and reports an external room sensor fault when using a remote Bosch NTC room sensor.
|
Remote Room Sensor Circuit Open/Short | View Details |
| E05 |
Thermostat displays E05 and indicates a floor sensor error (for hydronic or radiant floor applications).
|
Floor Temperature Sensor Fault | View Details |
| E06 |
Thermostat shows E06 and heating or cooling does not start; internal relay or triac fault indicated.
|
Output Relay/Triac Failure | View Details |
| E07 |
Thermostat displays E07 and shows no outdoor temperature; weather‑dependent functions disabled.
|
Outdoor Sensor / Weather Data Failure | View Details |
| E08 |
Thermostat shows E08 and reports low supply voltage; display may dim or reboot intermittently.
|
Low 24 V Control Voltage | View Details |
| E09 |
Thermostat displays E09 and cannot detect a required C‑wire; device may run only on batteries or not power up fully.
|
Missing or Unstable Common (C) Wire | View Details |
| E10 |
Thermostat shows E10 and indicates communication loss with Bosch boiler or heat pump over BUS/eBUS/EMS interface.
|
Digital BUS Communication Failure | View Details |
| E11 |
Thermostat displays E11 and indicates an internal memory or configuration error; settings may not save.
|
Non‑Volatile Memory (NVM) Corruption | View Details |
| E12 |
Thermostat shows E12 and touchscreen or buttons do not respond properly.
|
User Interface / Touch Panel Failure | View Details |
| E13 |
Thermostat displays E13 and indicates an internal temperature over‑limit; device may shut down temporarily.
|
Thermostat Overtemperature Protection | View Details |
| E14 |
Thermostat shows E14 and indicates a humidity sensor error; humidity reading is missing or unrealistic.
|
Internal Humidity Sensor Failure | View Details |
| E15 |
Thermostat displays E15 and indicates a schedule or clock synchronization error; timed programs may not run correctly.
|
Real‑Time Clock / Time Sync Failure | View Details |
| E16 |
Thermostat shows E16 and indicates a firmware update failure; device may be stuck on an update screen.
|
Firmware Update Interruption | View Details |
| E17 |
Thermostat displays E17 and indicates an internal sensor calibration error; temperature readings may be offset.
|
Internal Sensor Calibration Fault | View Details |
| E18 |
Thermostat shows E18 and indicates a geofencing/location service error; away/home automation not functioning.
|
Geolocation Service Failure | View Details |
| E19 |
Thermostat displays E19 and indicates an incompatible HVAC system configuration detected.
|
System Configuration Mismatch | View Details |
| E20 |
Thermostat shows E20 and indicates a security/authentication error with Bosch cloud services.
|
Cloud Authentication Failure | View Details |
| – |
Cooling runs but thermostat overshoots setpoint and room becomes too cold before shutting off.
|
Cooling Overshoot / Poor Temperature Control | View Details |
| – |
Heating runs but thermostat overshoots setpoint and room becomes too warm before shutting off.
|
Heating Overshoot / Poor Temperature Control | View Details |
| – |
Thermostat backplate or surrounding wall feels unusually warm to the touch.
|
Localized Overheating at Thermostat | View Details |
| – |
Thermostat calls for heat but Bosch boiler or furnace does not start; indicator shows heating demand active.
|
Heat Demand Not Reaching Equipment | View Details |
| – |
Thermostat cannot be added to Bosch smart home ecosystem or third‑party integrations (e.g., voice assistants) fail.
|
Integration / Pairing Failure | View Details |
| – |
Thermostat display is completely blank and does not power on.
|
No Power to Thermostat | View Details |
| – |
Thermostat does not call for cooling even when room is warm and setpoint is lower than room temperature.
|
No Cool Call from Thermostat | View Details |
| – |
Thermostat does not respond to Bosch app commands when away from home, but works locally.
|
Remote Access Failure | View Details |
| – |
Thermostat does not turn on the fan in ON mode, but fan runs during heating or cooling.
|
Fan Only Mode Not Working | View Details |
| – |
Thermostat fails to follow programmed schedule; heating/cooling does not change at scheduled times.
|
Schedule Execution Failure | View Details |
| – |
Thermostat frequently cycles the HVAC system on and off in short bursts (short cycling).
|
Short Cycling Due to Control Settings or Sizing | View Details |
| – |
Thermostat frequently disconnects from Wi‑Fi and goes offline in the Bosch app.
|
Intermittent Wi‑Fi Connectivity | View Details |
| – |
Thermostat is very slow to respond to touch or app commands; menus lag or freeze.
|
Performance Degradation / Software Lag | View Details |
| – |
Thermostat powers on but does not call for heat even when room is cold and setpoint is higher than room temperature.
|
No Heat Call from Thermostat | View Details |
| – |
Thermostat reboots randomly or the screen flickers during operation.
|
Unstable Power or Internal Reset | View Details |
| – |
Thermostat shows incorrect room temperature compared to other thermometers.
|
Temperature Reading Inaccuracy | View Details |
| – |
Thermostat shows large swings in humidity readings or humidity control is erratic.
|
Humidity Measurement or Control Instability | View Details |
No matching codes found
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