As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
COULD NOT CONTROL PRESSURIZATION IN AUTO OR MANUAL MODE WITH SEVERAL ATTEMPTS, DECLARED EMERGENCY AND DIVERTED TO ILM. COMPLIED WITH ENGINE RUN UP TO MAX CLIMB DETENT SEVERAL TIMES, UNABLE TO DUPLICATE DISCREPANCY AT THIS TIME. ALL WORK DONE PER GULFSTREAM-200 MAINTENANCE MANUAL CHAPTER 71-00-00, NO FURTHER ACTION REQUIRED AT THIS TIME.