As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT, NOTICED CREW OXYGEN GAUGE READING ZERO. IT WAS AT APPROXIMATELY 1550 PSI DURING PREFLIGHT. ACFT GROUNDED. REMOVED AND REPLACED CREW OXYGEN BOTTLE AND OPS CHECKED IAW AMM 12-15-21. PERFORMED LEAK CHECK OF OXYGEN LINE AND B-NUTS IAW AMM 35-12-00, NO LEAKS NOTED AT THIS TIME. CREW OXYGEN POD COMPLETED AND NO DEFECTS NOTED. FINAL INDICATED PRESSURE OF NEW BOTTLE 1950 PSI.