Cause : Encoder option comm loss comes when encoder feedback not used as actual feedback, or measured motor feedback lost (and parameter 90.45/90.55 is set to Warning).

1. Check that the encoder is selected as feedback source in parameter 90.41 or 90.51.
2. Check that the encoder interface module is properly seated in its slot.
3. Check that the encoder interface module or slot connectors are not damaged.
4. To pinpoint the problem, try installing the module into a different slot.
5. If the module is installed on an FEA-03 extension adapter, check the fiber optic connections.