As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EWR---CO2342, CREW REPORTED THAT PRESSURIZATION FLUCTUATED PLUS AND MINUS 1500 FEET PER MINUTE. UNCONTROLLABLE IN AUTO OR MANUAL MODES AIRCRAFT AIR RETURNED TO EWR AND LANDED UNEVENTFULLY. MAINTENANCE REMOVED AND REPLACED THE PNEUMATIC OUTFLOW VALVE (P/N 92185A010100, S/N 00239) IAW EMB135 MM 21-31-04 AND REMOVED AND REPLACED THE DIGITAL PRESSURE CONTROLLER (P/N 20996011100, S/N 01470) IAW EMB135 MM 21-31-01. OPS CHECKED GOOD. AIRCRAFT RELEASED FOR SERVICE.