What was found
IN DESCENT, VNAV DISENGAGED AND AUTOTHROTTLES CLICKED OFF AT 15,000'. FMA REVERTED INTO CWP. ABLE TO ENGAGE LEVEL CHANGE BUT NO VNAV. AUTOTHROTTLES SWITCH RE-ENGAGED BUT WAS NOT RESPONSIVE TO THRUST REQUIREMENTS. REFERENCE PREVIOUS SIMILAR WRITE UP PAGE 60146816. GROUNDED-YES. ACCOMPLISHED AN AUTOTHROTTLE FAULT REVIEW, REF B737-800 FIM 22-31/801, NO FAULTS NOTED. ACCOMPLISHED AN ADIRU FAULT REVIEW, REF FIM 34-21/801, NO FAULTS NOTED. ACCOMPLISHED CDS DEU FAULT REVIEW, REF FIM 31-62/801, FOUND FAULT 31-65050 "ALTITUDE DISAGREE" ON BOTH NR 1 AND NR 2 DEU'S AT 18,670 FT ON LEG 1. ACCOMPLISHED DFCS FAULT REVIEW, REF FIM 22-11/801. CHANNEL B HAD TWO INSTANCES OF FAULT 22-11822 "FMC DATA INV" AT 16000 FT AND 40000 FEET. BOTH ON LEG 1. ACCOMPLISHED HGS FAULT REVIEW, REF FIM 34-36/801, NO FAULTS NOTED. ACCOMPLISHED FIM 22-11/811 THROUGH STEP F(5), NO FAULTS NOTED. ACCOMPLISHED FIM 31-62/875 THROUGH STEP E, NO FAULTS NOTED. FOUND TAT PROBE DAMAGED AND HEAVILY CORRODED. REPLACED TAT PROBE, PER B737-800 AMM 34-21-06/401. OPERATIONS CHECK GOOD, PER SAME. ACCOMPLISHED TSR710254, REPLACED LT FMC IAW AMM 34-61-02/401 AND DFCS MCP, REF AMM 22-11-34/401. ACCOMPLISHED FMCS OPERATIONS TEST, OPERATIONS NORMAL, REF AMM 34-61-00-710-801. ACCOMPLISHED DFCS MCP REPLACEMENT TEST, GRP BITE 32, ALL TEST PASSED. ACCOMPLISHED DFCS LAND VERIFY TEST, GRP BITE 49, ALL TEST PASSED REF AMM 22-11-11/201.