What was found
DEBRIEFED CREW: ON TAKEOFF ROLL ABOUT 120 KTS, L ENG PRV EICAS YELLOW CAUTION IND OCCURED. CAUTION WENT AWAY BEFORE CREW CAN PERFORM QRH BUT EICAS STATUS PAGE MSG REMAINED. WHEN DESCENDING BELOW FL250-225 EICAS CAUTION CAME BACK. WHEN CREW LEVELED LVLD OFF & INCREASED ENG POWER, EICAS YELLOW CAUTION WENT AWAY BUT LOWER EICAS STATUS MSG REMAINED. APON RETURN FOUND PRV HARD FAULT ALONG WITH PRC. LEAK CHKD PRC, NO LEAKS FOUND AT PRC. R & R ENG 1 PRESSURE REGULATING VALVE (PRV) REF AMM 36-11-18-404-017-002. PERFORMED LEAK CHK WITH APU BLEED, LEAK CHKD GOOD. BIT ASCU, NO FAULTS NOTED. PERFRMD IDLE ENG RUN ON BOTH ENGS TO COMPARE EACH OTHER IAW AMM 71-00-00-795-003-N00. BOTH ENG BLEEDS ARE READING THE SAME. BIT ASCU POST ENG RUNS, NO FAULTS NOTED.