What was found
LT 10TH DUCT WARNING MESSAGE ILLUMINATED IN FLIGHT. C/W QRH, MESSAGE PERSISTS. DUCT (10TH) SHOWS RED BETWEEN LT 10TH SOV, PACK NR 1, 10TH ISOL VALVE, AND APU LCV ON ECS SYNOPTIC PAGE. AIRCRAFT REMOVED FROM SERVICE. R & R 10TH STAGE DUCTING LOOP B BLEED AIR SENSING ELEMENT, REF AMM 36-21-04. OPERATIONS CHECK GOOD. R & R BLEED LEAK DETECTION CONNECTOR P17WK, REF ESPM 20-17-11. OPERATIONS CHECK GOOD A/C FOR RETURN TO SERVICE.