As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING APPROACH IN IMC GPS PORTION OF THE FMS FAILED AND GAVE ERROR MESSAGE "GPS 1 NOT NAV". IT WAS DETERMINED THE COAXIAL CABLE AT THE BASE OF THE GPS ANTENNA HAD A POOR CONNECTION. THE COAXIAL CABLE WAS EASILY PULLED FROM THE COAX CONNECTOR. CONNECTOR REATTACHED TO THE COAX CABLE AND GROUND TESTED FINE.