Honeywell Error Code E2: Sensor Fault
How to Fix Honeywell Code E2
- Step 1: Turn the system off and then back on. This might reset the control board and clear a temporary error.
- Step 2: Check the air filter. A very dirty air filter can sometimes cause unusual temperature readings. Replace it if needed.
- Step 3: If the error persists after these steps, it's best to call a qualified HVAC technician for diagnosis and repair.
How to Reset Honeywell Code E2
- Remove the thermostat from its wall plate.
- Remove the batteries and wait 30 seconds.
- Reinsert the batteries and snap the thermostat back onto the wall plate.
- If the error persists, perform a factory reset through the menu: Menu > Preferences > Restore Factory Defaults.
Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.
What Does Honeywell Error Code E2 Mean?
The 'E2' error code on your Honeywell HVAC system indicates a problem with one of its temperature sensors. These sensors are like the system's eyes and ears, constantly monitoring temperatures to ensure everything is running smoothly and efficiently. When a sensor malfunctions or the control board loses communication with it, the system can't accurately regulate heating or cooling. This can lead to the unit shutting down, providing inconsistent temperatures, or running inefficiently. The E2 code specifically points to a fault in either the supply air temperature sensor or the return air temperature sensor. These sensors are thermistors, meaning their resistance changes with temperature. The control board reads these resistance changes to determine the air temperature.
Common Causes
- Faulty supply air temperature sensor
- Faulty return air temperature sensor
- Wiring issue between the sensor and the control board (loose connection, damaged wire)
- Corrosion on sensor terminals or control board connections
- Defective control board
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| System displays E2 error | Measure the resistance of the supply air temperature sensor at the control board. Disconnect the sensor wires before measuring. | A specific resistance value based on the air temperature. Refer to the Honeywell service manual for the correct resistance/temperature chart. |
| Supply air sensor resistance is out of range | Measure the resistance of the return air temperature sensor at the control board. Disconnect the sensor wires before measuring. | A specific resistance value based on the air temperature. Refer to the Honeywell service manual for the correct resistance/temperature chart. |
| Both sensors appear good | Inspect the wiring harness and connectors between the sensors and the control board for damage or loose connections. | Wiring and connections are intact and secure. |
| Wiring is good, but error persists | Check the voltage at the sensor connection on the control board. | Specific DC voltage, usually 5VDC. Refer to the Honeywell service manual. |
Applicable Honeywell Models
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Supply Air Temperature Sensor | — | — | — |
| Return Air Temperature Sensor | — | — | — |
| Control Board | — | — | — |
Related Codes on Same Models
Other codes that affect the same Honeywell model families as E2.
| Code | Description | Severity |
|---|---|---|
| E1 | Communication Error | Warning |
| E3 | EEPROM Error | Warning |
| E350 | Low Battery | Info |
| E351 | Equipment Fault | Warning |
| E352 | Sensor Open | Warning |
| E353 | Sensor Short | Warning |
| E4 | Short Cycle Protection | Warning |
| E5 | Wiring Error | Warning |