What was found
MCP ALTITUDE SELECTORS IS NOT WORKING PROPER AND CHANGING ALTITUDE ON ITS OWN. DIFFICULT OR IMPOSSIBLE TO MAKE SELECTIONS. ACFT GROUNDED. ACCOMPLISHED DFCS BITE TEST, NO FAULTS LOGGED. REMOVED & REPLACED DFCS MCP AS A PRECAUTION, IAW AMM 22-11-34/401. ACCOMPLISHED DFCS LRU INTERFACE TEST FOR MCP, IAW AMM 22-11-34/501 (GP 32), DFCS LAND VERIFY TEST, IAW AMM 22-11-00/201 (GP 49), AND HGS SYSTEM/SENSOR TEST, IAW SMM 34-36-00, OPS CHECKED NORMAL. ACFT LWMP STATUS REMAINS UPGRADED AT CAT3A AUTOLAND & HGS, CAT STATUS SCREW REFLECT SAME.