What was found
AUTOTHROTTLE WILL NOT REMAIN ENGAGED. LEFT THROTTLE DOES NOT MOVE WITH AUTOTHROTTLE-RIGHT THROTTLE SEEMS TO MOVE. GROUNDED - YES. INITIAL EVALUATION, PERFORMED A/T INTERACTIVE TESTS IAW B737-800 AMM 22-31-00-710-802. A/T ENGAGED AND DISENGAGED APPROPRIATELY WITH A/T ARM SWITCH ON MCP. SERVO MOTOR TEST MOVED THROTTLES AT FLUID RATE TOGETHER CONTINUOUSLY. RAN TEST SEVERAL TIMES. NO DEFECTS OBSERVED AT THIS TIME. REVIEWING THE IN-FLIGHT FAULT HISTORY, THE ONLY FLIGHT LEG FOR 30 FLIGHT LEGS WITH A/T FAULTS, WAS THE SAME TIME AND DATE THIS DEFECT WAS GENERATED. RATE MONITOR - ASM1 - MTX MSG 22-31687. PERFORMED DFCS LAND VERIFIY IAW AMM 22-00-01-730-801; ALSO REF AMM 22-11-00-700-801. ALSO PERFORMED HGS SYSTEM TEST IAW SMM 34-36-00 SEC 500, ALSO REF AMM 22-00-01-730-804. ALL TESTS PASS.