Thermostat displays E6 and outdoor temperature is not shown or is incorrect

Safety: Turn off power to the HVAC system before working on low-voltage wiring.

• Step 1 – Verify sensor presence: Confirm that an outdoor temperature sensor is actually installed. If not, disable the outdoor sensor option in the thermostat installer setup.
• Step 2 – Inspect sensor wiring: Locate the outdoor sensor near the condenser or on an exterior wall. Follow its two-conductor cable back to the thermostat or indoor unit and check for cuts, splices, or corrosion.
• Step 3 – Check connections: Tighten the sensor terminal screws at the thermostat or indoor control board. Ensure the wires are under the correct sensor terminals as shown on the wiring diagram.
• Step 4 – Test sensor resistance: With power OFF, disconnect the sensor and measure its resistance with a multimeter. Compare to Trane’s temperature/resistance chart. If readings are open, shorted, or far off, replace the sensor.
• Step 5 – Replace sensor if needed: Install a new Trane outdoor temperature sensor, route the cable away from high-voltage lines, and reconnect to the proper terminals.
• Step 6 – Clear error: Restore power and allow several minutes for the thermostat to recognize the sensor and clear E6.