As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 5844, CLE TO PVD - DURING CLIMB WHEN THE CREW CHECKED PRESSURIZATION, THE CPAM INDICATED ALL ZEROS. THERE WAS NO EICAS MESSAGE PRESENT. THE CREW LEVELED OFF, AND DECIDED TO RETURN TO FIELD. THE AUTOMATIC PRESSURIZATION SYSTEM WAS DEFERRED SINCE THE MANUAL MODE OPERATED NORMALLY. THE DEFERRAL WAS CLEARED ON 4/30/2009 IN STL WHEN A FUNCTION TEST OF THE PRESSURIZATION SYSTEM WAS PERFORMED IAW AMM 21-31-00. OPERATIONAL TEST GOOD, AND WERE UNABLE TO DUPLICATE DISCREPANCY.