As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOTS RECEIVED PAX OXY OFF MESSAGE BEFORE TAXI OUT, INDICATING LESS THAN 50 PSI IN PASSENGER OXYGEN BOTTLE SYSTEM. VERIFIED PAX BOTTLES WERE TURNED ON AND PRESSURES WERE READING NORMAL AT BOTTLES AND COCKPIT INDICATORS. VERIFIED FLOW FROM THERAPEUTIC OXYGEN PORT AS THIS UTILIZES PASSENGER BOTTLES. TROUBLESHOT INDICATION SYSTEM AND FOUND FAILED SWITCH, IDENTIFIER 95S4. WIRING WAS OK. SWITCH WAS REPLACED WITH NEW UNIT. INDICATION THEN NORMAL.