E202
Lennox
Outdoor Unit Communication Loss
Thermostat displays E202 indicating loss of communication with the outdoor unit; cooling or heat pump operation may be disabled.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Open or shorted communication wiring between Lennox smart thermostat and outdoor condensing unit or heat pump, Failed outdoor unit control board, Outdoor unit breaker tripped or disconnect pulled, Corroded or water-damaged low-voltage connections at outdoor unit
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.
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Repair Difficulty
Hard
4/5
Required Part
Lennox Outdoor Unit Control Board
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