As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT ENG OFF LIGHT ON & L ENG BLEED OFF EICAS MSG, WITH ENG RUNNING, ENG BLEED SW ON, LT & RT ISOLATION VALVES CLOSED. AC PACK SELECTED TO ON & PSI IS NORMAL. LT & RT PSI ARE DURING DESCENT. LEFT ENG BLEED OFF LIGHT IN DESCENT. PRSOV LOCKED CLOSED. REPLACED HPSOV. OPS OKAY.