Trane communicating thermostat shows 'Err 5', system may lock out certain modes

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.

Possible Causes

Incorrect equipment configuration in thermostat, Replaced component not properly recognized, Firmware mismatch between components

Steps to check:

Review installer setup: Enter the installer menu on the Trane communicating thermostat and verify that the correct furnace model and stages are configured.
Re-scan equipment: Use the thermostat's equipment discovery function (if available) to re-detect connected Trane components.
Power cycle: Turn off power to all communicating components, then restore.

When to call a professional: If Err 5 persists, a Trane dealer may need to update firmware or replace mismatched components.

Medium 3/5

Communicating Thermostat

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