As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
COCKPIT VALVE OPERATION EMITS OFFENSIVELY FOUL ODOR. RAN ACFT AND SMELLED A FAINT ODOR, ODOR SLOWLY DISSIPATED. REMOVED WATER SEPARATOR FILTER, FOUND DIRTY AND SAME ODOR. CLEANED FILTER AND RE-INSTALLED, RAN ACFT FOR 45 MINUTES WITH NO ODOR NOTED IAW MM 21-10-95.