As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI WHILE DEICING A/C L ENGINE ANTI-ICE EICAS 5PSI L ENGINE PACK ILLUMINATED ON EICAS, A/C THEN RETURED TO THE GATE AND MTX GROUNDED A/C, MTX THEN TROUBLESHOT PER FIM 36-20 FT 804 FOUND PRSOV VALVE STUCK CLOSED WITH ZERO PSI.REPLACED LH PRSOV PER AMM 36-11-09 ANTI ICE TEST ACCOMPLISHED PER AMM 30-21-00 NO DEFECTS NOTED A/C REMAINS NO ETOPS.AND RETURNED AC TO SERVICE.