A B767-300 AFTER MAINT WAS DISPATCHED ON AN OVERWATER ETOPS FLT WITHOUT VERIFICATION OF A POSITIVE FIX.

Narrative

ACFT ARRIVED WITH AN EICAS MESSAGE FOR AIR/GND DISAGREE AND R REVERSER ISOLATION VLV (STATUS MESSAGE). MAINT PAGES SHOWED CAPT'S PITOT; R PITOT; L-HAND PITOT; AUX; FO PITOT. BITE TESTS WERE PERFORMED BY MYSELF AND 2 OTHER TECHNICIANS ON THE PROX SENSOR ELECTRONICS UNIT PER MAINT MANUAL XXXX. AT FIRST; WE HAD A CARD FAULT (YYYY) ILLUMINATE. CARDS WERE SWAPPED PER THE MAINT MANUAL BUT THE FAULT DID NOT FOLLOW; INSTEAD IT DISAPPEARED AND THE PROX SENSOR ELECTRONICS UNIT SYS TEST ENDED SUCCESSFULLY. NO FAULTS WERE INDICATED FOR THE PREVIOUS FLTS. BY THE TIME WE RESET THE PROX SENSOR ELECTRONICS UNIT PER THE MAINT MANUAL AND RAN A COMPLETE SYS TEST; WHICH ALSO SHOWED NO FAULTS IN THE ENTIRE PROX SYS. MAINT CTL WAS NOTIFIED OF THE PROB AND HE SUGGESTED WE CHANGE THE PROX CARD YYYY AND SIGN OFF THE PROB. AFTER CONFERRING WITH ZZZ LINE ENGINEERING WE DECIDED TO REPLACE THE K206 AIR/GND SYS #2 RELAY AND RUN ANOTHER SYS TEST WHICH PASSED WITH NO FAULTS. THE ACFT WAS RELEASED AND RETURNED TO SVC. APPROX 1.5 HRS AFTER DEP I CHKED THE ACFT STATUS AND SAW THAT THE AIR/GND AND R REVERSER ISOLATION MESSAGE RETURNED JUST AFTER TKOF. THE ACFT CONTINUED TO ITS DEST.