As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER ENGINE START, LEFT DUCT PRESSURE READ 7 PSI. GROUNDED - YES. PERFORMED PNEUMATIC HEALTH CHECK ON NR 1 ENGINE PER AMM 36-11-00-710-802 AND FOUND "PRSOV" STUCK BETWEEN OPEN AND CLOSED POSITION. REMOVED AND REPLACED PRSOV PER AMM 36-11-04-400-801 AND BLEED AIR REGULATOR PER AMM 36-11-03 PERFORMED ENGINE BLEED AIR CROSSOVER CHECK PER AMM 36-11-710-801 ALL INDICATED DUCT PRESSURES IN LIMITS.