What was found
DURING TAXI FWD CARGO AIR INOP .DEFERRED SYSTEM FOR DEPARTURE IAW MEL -ABX-21-28-1.RETURNED AC TO SERVICE FOR FLIGHT. T/S PER FIM 21-28 FAULT TREE 810. NO FAULTS NOTED ON ZONE TEMP BITE TEST. "COND CARGO VALVE" MSG REMAINS AFTER RESET. LEADS TO BLOCK 42, (REPLACE FWD CARGO A/C SHUT OFF VALVE). DEACTIVATED SYSTEM PER MEL 21-28-1. DI REMAINS OPEN. R&R FWD CARGO VLV SHUTOFF VLV PER MM 21-28-01 OPS CHKD OK PERFORMED REACTIVATION PROCEDURES PER MEL MPM 21-28-1 PLACARD REMOVED AND DI CLEARED.