As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS AT 13000 FEET GOT A PRESSURIZATION WARNING HORN FOR APPROX 7 SECONDS. CABIN ALT 2500, DIFF PRESS 4.2 INCHES 300 FPM DOWN CABIN RATE. NO WARNING LIGHTS NOTED. MAINTENANCE PERFORMED FIM PROCEDURE 31-51-00-810-803 FOR INTERMITTANT HORN IN AIR. SWITCHES S1049 AND S1050 TEST NORMAL FROM PSEU. AURAL WARNING MODULE BITE CHECKS NORMAL IAW AMM 31-51-00. ALL TESTS NORMAL.