As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DIVERTED EARLIER IN DAY TO TYS DUE TO L ENG BLEED CAUTION MESSAGE. MAINT WORKED ON AIRCRAFT ALL DAY WHILE CREW WAITED AT HOTEL. DURING PART 91 REPO FLIGHT BACK TO ATL, CAUTION MESSAGE RETURNED. AIR RETURN TO TYS WAS RESULT. REMOVED AND REPLACED L 10TH STAGE HIGH PRESSURE SHUTOFF VALVE IAW AMM 36-12-05. OPS CHECK GOOD.