What was found
FLIGHT 2113. ON TAKEOFF, FLIGHT MODE DID NOT CHANGE FROM TO/GA TO CLIMB SEQUENCE. NAV BUTTON DID NOT WORK, VOR/ILS ONLY. NO EICAS MESSAGES OR CIRCUIT BREAKERS PRESENT TO INDICATE CAUSE. RETURNED TO FIELD LANDING UNEVENTFUL. REMOVED FROM SERVICE. NO ACTIVE FAULTS FOUND IN CMC. C/W AUTO PILOT OPS TEST IAW AMM TASK 22-11-00-710-802-A AND VHF NAV FUNCTION TEST IAW AMM TASK 34-32-00-720-801-A. OPS AND FUNC TESTS ARE GOOD. NO FAULTS FOUND. A/C WAS NOT DOWNGRADED. A/C REMAINS CAT 3 QUALIFIED. A/C STATUS PLACARD SHOWS GREEN CAT 3. MTX CONTROL NOTIFIED. RETURNED TO SERVICE. NO PARTS REPLACED.