As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI OUT , RH ENGINE BLEED VALVE OFF REGARDLESS OF THE POSITION AFTER STARTING ENGINE. AC RETURNED TO GATE(BTB) AND MTX GROUNDED AC , TROUBLE SHOT AND REPLACED RH PRSOV IAW AMM 36-11-09 OPS CK AND LEAK CK GOOD. INSPECTED HPSOV, PRC AND PRV LINES AND FITTING NO DEFECT FOUND. A/C REMAIN NO ETOPS. AND RETURNED AC TO SERVICE