How to Fix / Troubleshooting

Safety warning: Turn off power at the outdoor disconnect and indoor breaker before opening any panels.

1. Confirm outdoor unit power:
- Check the outdoor condensing unit or heat pump breaker in the main panel.
- Verify the outdoor disconnect is fully inserted and ON.
2. Inspect low-voltage wiring at outdoor unit:
- Remove the service panel on the Lennox outdoor unit.
- Locate the low-voltage terminal block (ABCD or R/C/Y/O/B depending on system).
- Check for loose, corroded, or broken wires; tighten terminals and clean corrosion.
3. Check cable condition:
- Visually inspect the thermostat cable run between indoor and outdoor units for damage from landscaping, pets, or UV exposure.
- Repair or replace any damaged cable sections.
4. Power cycle and recheck:
- Restore power to both indoor and outdoor units.
- Allow the thermostat to reboot and attempt to re-establish communication.
5. If E202 remains:
- The outdoor control board or communication module may be defective.
- Contact a Lennox service technician to test the board and replace if necessary.

Thermostat displays E202 indicating loss of communication with the outdoor unit; cooling or heat pump operation may be disabled.

Possible Causes