Thermostat shows E2 and humidity reading is missing or stuck at 0%/100%

Safety first: Shut off power to the HVAC system at the breaker before removing the thermostat.

• Step 1 – Power cycle: Remove the thermostat from the wall plate for 30 seconds, then reinstall. Check if E2 clears.
• Step 2 – Visual inspection: Remove the thermostat and locate the humidity sensor (often a small module or chip near vent slots). Check for signs of condensation, corrosion, or dust buildup.
• Step 3 – Clean sensor: If accessible, gently blow dry air across the sensor or use a soft brush to remove dust. Do not use liquid cleaners.
• Step 4 – Check harness: If the humidity sensor is on a small daughterboard or harness, ensure the connector is fully seated and the wires are not pinched or broken.
• Step 5 – Replace sensor module: If E2 persists and the sensor is modular, replace the humidity sensor module with a compatible iComfort part. If integrated, the entire display or main control board may need replacement.
• Step 6 – Verify operation: Restore power and compare humidity reading to a known good hygrometer in the same room.