Thermostat shows E2 and may lock out cooling operation; outdoor temperature reading is missing or incorrect if displayed.

Safety first: Turn off power to the outdoor unit and indoor unit before working on low‑voltage wiring.

• Locate the outdoor sensor: Payne systems that support outdoor temperature often use a small probe sensor mounted near the outdoor condenser or on an exterior wall. Trace the two‑wire cable back to the thermostat or indoor control board.
• Inspect wiring: Look for cuts, crushed insulation, or corroded connections at wire nuts or terminal blocks. Repair any damaged sections and remake corroded connections.
• Check sensor resistance (advanced): With power off, disconnect the two sensor wires at the thermostat or control board. Use a multimeter to measure resistance across the sensor. Compare to the Payne sensor chart (typically around 10kΩ at 77°F for many NTC sensors). A reading of 0Ω (short) or infinite (open) indicates a bad sensor.
• Verify configuration: In the installer setup menu of the Payne smart thermostat, confirm that the outdoor sensor option is enabled only if a sensor is installed, and that the correct sensor type is selected.
• Replace sensor if faulty: If resistance is out of range, replace the Payne outdoor temperature sensor with the specified part. Route the new cable away from high‑voltage lines.
• If E2 remains: With a known‑good sensor and wiring, the thermostat's sensor input circuit may be defective. Replace the thermostat.