!!
critical Garrison
Error Code Err
The unit is in an error condition and may be malfunctioning.
? What Causes This
Internal fault or malfunction detected by the unit.
✓ How to Fix It
Replace the CO alarm immediately, as it will not detect CO while in this state.
Source: page 13 of the official manual
From the manual
This error code appears in:
Garrison 043 6119 2