What was found
FLT 403 - MEX-NYC - AIRCRAFT RETURNED TO MEX AS CONSEQUENCE OF NAVIGATIONAL INSTRUMENTS FAIL. DURING CLIMBING THE NR 2 SYMBOL GENERATOR MALFUNCTIONED. BOTH EFIS WERE SWAPPED, OPERATION REESTABLISHED, BUT AFTER BOTH SYMBOL GENERATORS AND BOTH FMA OUT OF SERVICE, FLIGHT COMPUTERS WERE CHANGED WITHOUT SOLUTION. AT RON MEX 04/05 THE FAIL WAS FOUND IN THE AHRS 2, IT WAS REPLACED IAW MM 34-21.00, TESTS OK. (M)