As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK, 2L DOOR HAD A LARGE AIRLEAK AUTO CONTROLLER DID NOT HAVE OUTFLOW VALVE FULL CLOSED. GOT CABIN ALT WARN LIGHT CABIN WAS AT 10000 FT/BIT AUTO CONTROLLER 1 FAULTED GROUND SWITCH. PRESSURIZED A/C PER M/M, NO DOOR LEAKS NOTED. FOUND LOOSE SCREW HAD FALLEN INTO RELAY R2-4 SHORTING TERMINALS D1 AND D2. REPLACED RELAY. PERFORMED BIT TEST PER PER M/M. ALL CKS GOOD. PERFORMED TEST OF SYS AND FOUND SYS TESTS NORMAL.