As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMBING THROUGH 6000 FEET CABIN ALTITUDE HORN SOUNDED. WARNING HORN CAME ON AND OFF INTERMITTENTLY, AND EVENTUALLY WENT OFF. RETARD DISPLAY IN HUD ALSO EVENTUALLY WENT OFF. NO EMERGENCY WAS DECLARED, AND THE FLIGHT RETURNED WITHOUT FURTHER INCIDENT. ACCOMPLISHED CABIN PRESSURIZATION GROUND TEST AND FOUND BOTH PRESSURE CONTROLLERS WORKING NORMAL IAW AMM 21-31-00.