E15 displayed and thermostat reports sensor calibration error; temperature or humidity readings appear obviously wrong.

Safety: Turn off power before removing the thermostat if internal inspection is needed.

• Step 1 – Compare readings: Place a reliable thermometer/hygrometer near the thermostat and compare readings. Note the difference.
• Step 2 – Adjust calibration: In the installer or advanced settings menu, use the temperature offset and/or humidity offset feature to correct minor differences (typically ±5°F or ±10% RH).
• Step 3 – Factory reset: If offsets are extreme or E15 persists, perform a factory reset to clear any corrupted calibration data.
• Step 4 – Check for interference: Ensure no high‑voltage lines are routed directly behind the thermostat and that it is not mounted on metal that could affect sensor performance. Relocate if necessary.
• Step 5 – Replace thermostat module: If readings remain far off and E15 continues, replace the thermostat display/control module with integrated sensors.