What was found
AFTER ENGINE START EICAS MSG LEFT AND RIGHT EEC MODE DISPLAYED WITH CA'S PITOT STATIC INSTRUMENTS ALL DISPLAYED OFF FLAGS- SELECTED ALL DATA AIR SWITCH/FIXED. AIRCRAFT RETURNED TO GATE AND GROUNDED BY MAINTENANCE. EEC MONITOR FAULT SHOWED NO FAULTS ON RIGHT AND UNRELATED FAULT ON LEFT (352-28) NO FAULTS ON BPCU. NO FAULTS ON WEU. CYCLED LH ADC CB AND ALL FLAGS CLEARED. ACCOMPLISHED BOTH ENGINE IDLE RUN IAW B767 AMM 71-00-00. CYCLED LOUD AROUND TO BOTH GENERATORS WITH NO FAILURES. OPS CHECK GOOD. A/C REMAINS NO ETOPS. AIRCRAFT RETURNED TO SERVICE.