What was found
FLIGHT 2015. DISPLAYS 2,3, AND 4 WENT DARK IN FLIGHT. CAME BACK AS EICAS ON ALL DISPLAYS. WAS ABLE TO REVERT DISPLAY 4 TO MFD. REMOVED FROM SERVICE. INTERROGATED CMC AND FOUND NO FAULT CODES. PERFORMED DISPLAYS OPS TEST REF E175 AMM 31-61-00-710-801-A AND MANUAL DISPLAYS REVERSION OPS TEST REF E175 AMM 31-61-02-710-801-A. BOTH OPS TEST PASSED. NO FURTHER DEFECTS NOTED. AIRCRAFT REMAINS CAT III. RETURNED TO SERVICE. NO PARTS REPLACED.