How to Fix / Troubleshooting

Safety warning: Turn off power to the thermostat and zone panel (if present) before servicing sensor wiring.

1. Confirm sensor presence and location:
- Locate the Lennox outdoor temperature sensor, usually mounted on the north or shaded side of the home.
- Ensure it is not in direct sunlight or near dryer vents or exhausts.
2. Inspect wiring:
- Check the sensor cable for cuts, abrasions, or rodent damage.
- Verify tight connections at both the sensor and the thermostat/zone panel terminals.
3. Test sensor:
- Disconnect the sensor and measure resistance; compare to Lennox temperature/resistance chart.
- If reading is open, shorted, or far out of range, replace the sensor.
4. Reconfigure thermostat if no sensor is used:
- If the system does not use an outdoor sensor, disable the feature in the thermostat installer settings to clear E222.

Thermostat shows E222 indicating remote outdoor temperature sensor fault; outdoor temperature reading is missing or incorrect.

Possible Causes