As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: ENGINE 2 BLEED FLUCTUATES 24 - 38 PSI AT 20 CYCLES PER MIN. RESULTS IN CONSTANT CABIN PRESSURE FLUCTUATIONS, -250 TO +150 FPM..REPLACED #2 ENGINE PRESSURE REGULATING VALVE AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 36-11-52.