Err 2
Trane
Outdoor Unit Communication Fault (in dual fuel or integrated systems)
Trane communicating thermostat shows 'Err 2', furnace may not respond
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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 communication wiring to outdoor unit, Faulty outdoor control board, Miswired ABCD at outdoor unit, Power loss to outdoor unit
How to Fix / Troubleshooting
Safety: Turn off power to both indoor and outdoor units before servicing.
Steps to check:
- Verify outdoor power: Ensure the outdoor disconnect is on and breaker is not tripped.
- Inspect ABCD wiring at outdoor unit: Confirm correct color-to-terminal matching and tight connections.
- Check cable continuity: If accessible, test continuity of the communication cable between indoor and outdoor units.
When to call a professional: Outdoor control board or communication bus diagnostics are best handled by a Trane technician.
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Repair Difficulty
Hard
4/5
Required Part
Outdoor Unit Control Board
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