As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
VENT AVNCS SYS FAULT AFTER TAKEOFF. OUTLET VALVE HAD AMBER X'S. LOUD SQUEAL HEARD. COULD NOT PRESSURIZE. RETURNED TO KIAH. BURNED FUEL TO LAND UNDER MGLW. TOUCHDOWN @ 170,900LBS ( SKIN AIR OUTLET VALVE ) PERFORMED OPS CK OF AEVC IAW AMM 21-26-00. FAULT CLEARED. OPS CK GOOD. THIS CLOSES DMI# 245229701. MOC NOTIFIED PLACARD REMOVED. LOG UPDATED