As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED DUE TO: CABIN ALTITUDE LIGHT ILLUMINATED ON CLIMB OUT; AIRCRAFT AIR INTERRUPTED BACK TO AND LANDED SAFELY AT MEX. ACCOMPLISHED PRESSURIZATION SYSTEM GROUND TEST, PER AMM 21-31-00-700-802. NO FAULT NOTED. AS WELL AS ACCOMPLISHED PRESURIZATION SYSTEM MANUAL MODE TEST, PER AMM 21-31-00-710-801. NO FAULT NOTED.