Thermostat displays E02 and cannot detect indoor temperature; screen may show dashes instead of a temperature reading.

Safety: Turn off power to the HVAC system at the breaker before removing the thermostat from the wall.

• Step 1 – Power cycle: Turn off power for 60 seconds, then restore. If E02 clears temporarily and returns, the sensor is marginal.
• Step 2 – Check for environmental issues: Ensure the thermostat is not installed over a hot air register, in direct sunlight, or on an exterior wall with temperature extremes. Correct installation issues if present.
• Step 3 – Inspect for moisture or contamination: Remove the thermostat from the sub‑base. Look for condensation, corrosion, or dust buildup on the sensor area (usually a small component near ventilation slots). Gently blow out dust with dry compressed air. Do not use liquids.
• Step 4 – Factory reset: From the menu, perform a factory reset (note: this will erase schedules and custom settings). Reconfigure and check if E02 returns.
• Step 5 – Replace thermostat module: The internal sensor is typically integrated into the main PCB and not field‑replaceable. If E02 persists, replace the thermostat display/control module or the entire thermostat.