Thermostat displays E9 and will not complete Wi‑Fi setup or loses connection repeatedly

Note: This error affects connectivity but not basic heating/cooling control.

• Step 1 – Check Wi‑Fi signal: Use a phone at the thermostat location to verify strong Wi‑Fi signal. If weak, move the router or add a Wi‑Fi extender.
• Step 2 – Reset network settings: In the thermostat menu, forget the current network and re-enter the SSID and password. Ensure the router uses WPA2 or WPA3 security and 2.4 GHz if required by the thermostat.
• Step 3 – Power cycle router and thermostat: Reboot the router, then reboot the thermostat.
• Step 4 – Firmware update via USB (if supported): Some Trane smart thermostats allow firmware updates via USB or SD card. Install the latest firmware from Trane’s support site.
• Step 5 – If E9 persists: The Wi‑Fi module inside the thermostat is likely defective. Replacement of the thermostat is usually required.