What was found
CREW REPORTS ON TAXIOUT GOT RT ENG IDG VALVE EICAS MESSAGE. VALVE LOCKED OUT PER MEL 7521D. ACP COMPONENT RESISTANCE CHECK AND OPERATIONAL TEST WITH EXTERNAL AIR USING MIPS PW 4000 IDG AOC TS. VALVE OPERATED WITH NO MSG. ACCOMPLISHED BLOCK 6 POWER RUN. VERIFIED VALVE OPENED AND CLOSED OUT TEMP COOLED. NO STATUS MSG ALSO REPLACED GCU AND RELAY K1031. ALL OPERATIONS CHECKED ON RUN. BPCU CLEAN AFTER RUN. DID NOT REPLACE K1031, BUT REPLACED K971 (R IDG AIR COOLER VLV RELAY).