What was found
IAS, MACH SPEED SELECTOR WAS FROZEN WITH SPEED AT 157. ACFT GROUNDED. PERFORMED FIM 22-32, TASK 803, DFCS BITE SHOWS FAULT 22-4003. PERFORMED MCP PANEL TEST IAW FIM 22-11, TASK 803 ALL TESTS PASSED. BUT IAS/MACH KNOB STILL INOPERATIVE. REMOVED AND REPLACED DFCS MCP IAW AMM 22-11-34, ALL TESTS PASSED, IAS/MACH CONTROL KNOB OPS NORMAL AIRCRAFT OK FOR SERVICE.