Ecobee
Ecobee 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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AUX
Thermostat displays a warning that auxiliary heat is running excessively or not responding.
Auxiliary Heat Control / Response Fault
E1
Thermostat displays E1 and cannot communicate with the HVAC equipment.
Equipment Interface Module Communication Failure
E2
Thermostat displays E2 and indicates a problem with the outdoor temperature or remote sensor.
Remote Sensor / Accessory Sensor Communication Fault
E3
Thermostat displays E3 and cannot detect the HVAC equipment type or configuration.
Equipment Configuration / Detection Error
E4
Thermostat displays E4 and indicates a problem with the internal temperature sensor.
Internal Thermostat Temperature Sensor Failure
E5
Thermostat displays E5 and reports a problem with the Wi‑Fi or internet connection.
Wi‑Fi Connectivity Failure
E6
Thermostat displays E6 and cannot detect the outdoor temperature from a heat pump or external sensor.
Outdoor Temperature Sensor / Heat Pump Communication Fault
E7
Thermostat displays E7 and reports a problem with the humidity sensor.
Internal Humidity Sensor Failure
E8
Thermostat displays E8, indicating a problem with the Power Extender Kit (PEK).
Power Extender Kit (PEK) Wiring or Detection Error
E9
Thermostat displays E9, reporting an internal hardware fault.
Internal Hardware or Logic Board Failure
ERR_SENSOR_OPEN
Thermostat reports that a remote room sensor is not detected or shows 'N/A'.
Open-Circuit Remote Sensor (Wired) or Offline SmartSensor
ERR_SENSOR_SHORT
Thermostat reports that a remote room sensor is shorted or shows an impossible temperature (e.g., -40°F or 200°F).
Short-Circuit Remote Sensor (Wired)
H1
Thermostat displays H1, indicating a high temperature detected at the thermostat.
Over-Temperature Condition at Thermostat
H2
Thermostat displays H2, indicating a low temperature detected at the thermostat (freeze warning).
Low-Temperature / Freeze Condition at Thermostat
LOW_BATTERY_SENSOR
Thermostat or app reports a low battery on an Ecobee SmartSensor.
SmartSensor Low Battery Condition
NO_COOL
Ecobee displays 'No cool' or 'Cool not responding' when calling for cooling.
Cooling Equipment Non-Response
NO_FAN
Ecobee calls for the fan, but the indoor blower does not run.
Indoor Blower Fan Non-Response
NO_HEAT
Ecobee displays 'No heat' or 'Heat not responding' when calling for heat.
Heating Equipment Non-Response
W1
Thermostat displays a warning that the furnace is not responding when a heat call is initiated.
Heat Call Not Energizing W Circuit
Y1
Thermostat displays a warning that the AC or heat pump is not responding when a cooling call is initiated.
Cool Call Not Energizing Y Circuit
Symptom
Dehumidifier connected to ecobee does not turn on or remove moisture
Dehumidifier Control / Wiring Fault
Symptom
The room temperature overshoots the setpoint by several degrees before the system shuts off.
Thermostat Overshoot / Differential or Sensor Placement Issue
Symptom
The thermostat is powered but does not activate heating or cooling.
Configuration or Control Output Failure
Symptom
The thermostat or the wall area feels unusually warm to the touch.
Localized Overheating at Thermostat Location
Symptom
The thermostat reboots randomly or frequently restarts on its own.
Intermittent Power or Firmware Instability
Symptom
The thermostat screen is completely blank and unresponsive.
Loss of 24V Control Power to Thermostat
Symptom
The thermostat short cycles the HVAC system (frequent on/off every few minutes).
Short Cycling Due to Thresholds or Equipment Issues
Symptom
The thermostat shows 'Calibrating: Heating and Cooling Disabled' for an extended period.
Extended Sensor Calibration / Power-Up Delay
Symptom
Thermostat calls for heating and cooling at the same time or rapidly switches between them
Improper Heat/Cool Changeover or Reversing Valve Configuration
Symptom
Thermostat does not detect or pair with SmartSensors
SmartSensor Pairing / RF Communication Failure
Symptom
Thermostat does not power on after installation when only two wires are available
Insufficient Conductors / Missing Common Wire
Symptom
Thermostat frequently displays 'Aux heat running', and energy bills are high
Excessive Auxiliary Heat Usage
Symptom
Thermostat frequently displays 'Equipment offline' or 'Equipment not responding' messages
Intermittent Low-Voltage Control Circuit Fault
Symptom
Thermostat loses Wi-Fi connection intermittently, but HVAC still runs
Intermittent Network Connectivity
Symptom
Thermostat shows 'Fan running' even when there is no active heating or cooling call
Continuous Fan Operation
Symptom
Thermostat shows humidity, but whole-home humidifier does not run when expected
Humidifier Control Output Failure
Symptom
Thermostat shows incorrect time or schedule does not run at expected times
Time Synchronization / Time Zone Misconfiguration
Symptom
Thermostat shows large temperature swings between different rooms despite SmartSensors installed
Ineffective Room Averaging / Sensor Placement Issue
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| AUX |
Thermostat displays a warning that auxiliary heat is running excessively or not responding.
|
Auxiliary Heat Control / Response Fault | View Details |
| E1 |
Thermostat displays E1 and cannot communicate with the HVAC equipment.
|
Equipment Interface Module Communication Failure | View Details |
| E2 |
Thermostat displays E2 and indicates a problem with the outdoor temperature or remote sensor.
|
Remote Sensor / Accessory Sensor Communication Fault | View Details |
| E3 |
Thermostat displays E3 and cannot detect the HVAC equipment type or configuration.
|
Equipment Configuration / Detection Error | View Details |
| E4 |
Thermostat displays E4 and indicates a problem with the internal temperature sensor.
|
Internal Thermostat Temperature Sensor Failure | View Details |
| E5 |
Thermostat displays E5 and reports a problem with the Wi‑Fi or internet connection.
|
Wi‑Fi Connectivity Failure | View Details |
| E6 |
Thermostat displays E6 and cannot detect the outdoor temperature from a heat pump or external sensor.
|
Outdoor Temperature Sensor / Heat Pump Communication Fault | View Details |
| E7 |
Thermostat displays E7 and reports a problem with the humidity sensor.
|
Internal Humidity Sensor Failure | View Details |
| E8 |
Thermostat displays E8, indicating a problem with the Power Extender Kit (PEK).
|
Power Extender Kit (PEK) Wiring or Detection Error | View Details |
| E9 |
Thermostat displays E9, reporting an internal hardware fault.
|
Internal Hardware or Logic Board Failure | View Details |
| ERR_SENSOR_OPEN |
Thermostat reports that a remote room sensor is not detected or shows 'N/A'.
|
Open-Circuit Remote Sensor (Wired) or Offline SmartSensor | View Details |
| ERR_SENSOR_SHORT |
Thermostat reports that a remote room sensor is shorted or shows an impossible temperature (e.g., -40°F or 200°F).
|
Short-Circuit Remote Sensor (Wired) | View Details |
| H1 |
Thermostat displays H1, indicating a high temperature detected at the thermostat.
|
Over-Temperature Condition at Thermostat | View Details |
| H2 |
Thermostat displays H2, indicating a low temperature detected at the thermostat (freeze warning).
|
Low-Temperature / Freeze Condition at Thermostat | View Details |
| LOW_BATTERY_SENSOR |
Thermostat or app reports a low battery on an Ecobee SmartSensor.
|
SmartSensor Low Battery Condition | View Details |
| NO_COOL |
Ecobee displays 'No cool' or 'Cool not responding' when calling for cooling.
|
Cooling Equipment Non-Response | View Details |
| NO_FAN |
Ecobee calls for the fan, but the indoor blower does not run.
|
Indoor Blower Fan Non-Response | View Details |
| NO_HEAT |
Ecobee displays 'No heat' or 'Heat not responding' when calling for heat.
|
Heating Equipment Non-Response | View Details |
| W1 |
Thermostat displays a warning that the furnace is not responding when a heat call is initiated.
|
Heat Call Not Energizing W Circuit | View Details |
| Y1 |
Thermostat displays a warning that the AC or heat pump is not responding when a cooling call is initiated.
|
Cool Call Not Energizing Y Circuit | View Details |
| – |
Dehumidifier connected to ecobee does not turn on or remove moisture
|
Dehumidifier Control / Wiring Fault | View Details |
| – |
The room temperature overshoots the setpoint by several degrees before the system shuts off.
|
Thermostat Overshoot / Differential or Sensor Placement Issue | View Details |
| – |
The thermostat is powered but does not activate heating or cooling.
|
Configuration or Control Output Failure | View Details |
| – |
The thermostat or the wall area feels unusually warm to the touch.
|
Localized Overheating at Thermostat Location | View Details |
| – |
The thermostat reboots randomly or frequently restarts on its own.
|
Intermittent Power or Firmware Instability | View Details |
| – |
The thermostat screen is completely blank and unresponsive.
|
Loss of 24V Control Power to Thermostat | View Details |
| – |
The thermostat short cycles the HVAC system (frequent on/off every few minutes).
|
Short Cycling Due to Thresholds or Equipment Issues | View Details |
| – |
The thermostat shows 'Calibrating: Heating and Cooling Disabled' for an extended period.
|
Extended Sensor Calibration / Power-Up Delay | View Details |
| – |
Thermostat calls for heating and cooling at the same time or rapidly switches between them
|
Improper Heat/Cool Changeover or Reversing Valve Configuration | View Details |
| – |
Thermostat does not detect or pair with SmartSensors
|
SmartSensor Pairing / RF Communication Failure | View Details |
| – |
Thermostat does not power on after installation when only two wires are available
|
Insufficient Conductors / Missing Common Wire | View Details |
| – |
Thermostat frequently displays 'Aux heat running', and energy bills are high
|
Excessive Auxiliary Heat Usage | View Details |
| – |
Thermostat frequently displays 'Equipment offline' or 'Equipment not responding' messages
|
Intermittent Low-Voltage Control Circuit Fault | View Details |
| – |
Thermostat loses Wi-Fi connection intermittently, but HVAC still runs
|
Intermittent Network Connectivity | View Details |
| – |
Thermostat shows 'Fan running' even when there is no active heating or cooling call
|
Continuous Fan Operation | View Details |
| – |
Thermostat shows humidity, but whole-home humidifier does not run when expected
|
Humidifier Control Output Failure | View Details |
| – |
Thermostat shows incorrect time or schedule does not run at expected times
|
Time Synchronization / Time Zone Misconfiguration | View Details |
| – |
Thermostat shows large temperature swings between different rooms despite SmartSensors installed
|
Ineffective Room Averaging / Sensor Placement Issue | View Details |
No matching codes found
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